Is there any reason to keep my medical records from my mom's terminal cancer?

I agree with PatriciaAS, but want to add that you may wish to speak with an accountant or tax attorney in regards to your deceased Mom's bills, etc. Those professionals may be able to shed light on how long and for what reasons you may want to hang on to some of her "papers" for now.

I would keep them as long as your keep income tax records. I believe this is seven years. Then would toss and like you said only keep things for the history for future generations.