When does a caregiver know it is time to commit a person to long term care or assisted living?

When the caregiver starts wondering or asking themselves when is the right time.

I think this is different in every situation. It depends not only on the level of functioning of the care recipient but the availability of funds for long term care and of potential unpaid caregivers if the person remains at home. It also depends on whose perspective you are considering. From the point of view of the caregiver, it may be well past time for the senior to enter residential care, while the senior may view it very differently.

If you shared more about the situation you have in mind, it would be easier to respond more helpfully.

Usually a person doing the caring will know that the love one needs a higher level of care, as you are ready to crash and burn from total exhaustion.

Note that almost 40% of a single family caregiver will die leaving behind the person they were caring for. Some love ones need around the clock care, 168 hours a week, as they go through their various phases of Alzheimer's/Dementia [as per your profile].  The average human cannot do that without some help.

So unless you wake up ready for this job each day, enjoying it, etc. it times to either bring in paid professional caregivers to help you or a move to either Assisted Living/Memory Care or long-term-care.