When is it time to give up pureed foods?

Karsten,
Your father should be given a swallowing evaluation by a speech therapist.

If your dad has had aspiration pneumonia a couple of times, something isn't working to get the food from the mouth to the stomach. An upper G.I. (an X-Ray while swallowing barium, a contrast medium) might show what the problem is. You'll know more after the tests.

Who ordered the pureed food?
Usually it IS pretty vile stuff. Texture is a big part of food, so is cutting up and moving or mixing it while eating. Smell too, plays a part in appetite. Pureed food lacks all that. 

What you can do is increase the flavor of the food (seasonings or a pinch of salt if authorized by the doctor).
Also, try having him "drink" it through a large straw instead of using a spoon. Make sure it's just warm, not hot. Use ThickIt brand of liquid thickener if he chokes on thin liquids. You can make the liquid as thick as necessary. It has no flavor. Amazon sells it.

If he HAS to keep on pureed diet, ask him what you can do to make the food more palatable.
You can add protein powder to a chocolate milkshake, cream soups are good, etc.

If he's going to do his own thing (eat regular food), get tips from the therapist doing the swallow eval, like chewing thoroughly, eating slowly, finish and swallow one bite before taking another, thinking while swallowing, swallowing using the dominant side of the body, etc. 
IMO, the risk of aspiration goes up marginally when eating solid food. But, if you utilize the techniques above, you can lessen the risk.

Heck, it's a hard call. I don't know what I'd do either. I love food and I enjoy all aspects of food.
Be as creative as you can be. Good luck.

Karsten, we've faced the same issue. The first bout with dysphagia occurred 15 years ago, under different circumstances than now, and was eventually resolved so that normal eating could be resumed. This time is different, as are the options.

Speech exercises can still be done, pureed food can be the given menu, but it does take more effort to make it palatable, perhaps visually more than being tasty. One of the biggest issues is the presentation. A pile of mush can turn off anyone's appetite.

The options as explained to us by a speech pathologist and a PCP physician who treated in the hospital, are (a) to continue on the bland, pureed and thickened liquids diet, using experimental and clever food prep to make it more palatable, or (b) just eat normally but expect that aspiration pneumonia may likely occur.

I did try some pureed coffee just to see what it was like; it was barely drinkable. Blah.

Through hospitalizations and rehab stints, I've realized that the good dieticians can make the food more palatable. The one in the current facility actually pureed cannolis, and they were good. Some of the meats, such as the ham today, was really more like mechanical soft than a full puree; it's often hard to puree some meats.

The current facility also has a much more varied menu than another rehab facility we've experienced, but not as tasty food as the hospital.

I don't think anyone can really quantify the risk of aspiration and how it will increase because so much depends on the individual's level of dysphasia.

A scopolamine patch has been tried for my father, to cut the phlegm and make it easier to cough up when choking on food. I was initially very reluctant to try it b/c of the side effects I read about when researching it.

I can see that it does thin the secretions, but the side effects are intense: initial confusion to a level I've never seen, first time ever for fidgeting, as well as recognition that something was amiss and expressed frustration over the lack of mental clarity.

Now the confusion is gone but exhaustion is everpresent, and sleeping has increased several fold. Food consumption has dropped to almost nothing. Water consumption has increased, perhaps because of the dry mouth side effect.

I'm at the point that I don't see the benefit of thinning the secretions but suffering from such an intense loss of appetite that weight declines are inevitable. Weight loss is intense, as is increased weakness and lack of interest in food.

I'm going to ask to D/C it tomorrow.

GA said
"but it does take more effort to make it palatable, perhaps visually more than being tasty. One of the biggest issues is the presentation".
It is an unfortunate reality in institutional care that the pureed food is generally an afterthought. I've often thought that it would be better if an entirely different menu was available for those with modified diets because some foods just don't turn out very well - pureed salad anyone? - while others can seem much more "normal" (soups, stews, certain mashed veggies, pureed meats made into a rich gravy etc). I would ask if there is any possibility of some common sense accommodation like offering a regular diet but modifying only problematic menu items (tough/dry meats for example) BUT I'm not sure you could trust them to follow through even if they agreed to try.

Have you tried the food, is it totally the texture or is it just plain bad?

That's what my dad, who suffered from PD, did. He 'graduated' to mechanical soft, but that didn't last. After that we were just as careful as we could be.

talkey, I think you had said your dad was in a MC? Did they do this "careful" strategy at the MC?

Adding a few comments after reading Sue's post: We were advised that straws absolutely cannot be used because of the possibility of sipping more into the mouth before realizing that it's too much to deal with. Spoons 1/2 or 3/4 full are safer. Regular tableware spoons are appropriate; wider and soup spoons are out.

Chin tucks when eating and swallowing are recommended. Eating should be stopped when coughing starts, until the mouth is cleared of food.

Swabs (spongy tips on sticks like lollipops) can be used to clean unswallowed food out of the mouth.

There are 2 levels of thickening liquids: honey thick or nectar thick. A videoscopic swallow followed by a speech pathologist's recommendation will indicate which is appropriate.

My father's diet forbids milkshakes, especially ones that are melted. He has thickened water (with honey, as I was told by a speech pathologist back in 2004 that honey stimulates the swallowing muscles), thickened cranberry and thickened orange juice. I'm going to ask permission to try a thickened honey lemon drink and thickened cider.

My mother went to the hospital for what was termed a swallow test when she gagged on the puréed foods. She was deemed to be at too high a risk for aspiration to continue using them. Maybe it’s time to see where your dad exactly stands on his ability to eat and swallow food? The swallow test uses various consistencies to see how it is swallowed and goes down and the aspiration risk. Good to have a real idea how he’s doing

Daughter1930 raised an important issue, i.e., when pureed foods aren't the solution. Based on repeated advice from speech pros, the next step is either intubation or PEG tube, and some doctors insisted on both.

Been through that; it's definitely not an option again.