What do mean by ?
I hope I get it wrong, how long your life can be isn't something you can PLAN unless you intentionally do something with it.

I know it is hard being a mother always worry about their children even after they grow up, but you have to let go, you can't add more pressure to yourself that is beyond your ability unless you sure you can handle it. Let them learn on their own and take responsibility of their own actions even if your son is suffered from Bipolar, otherwise they will never learn. All you can do is advice what he could do and asked him to seek help from social service if necessary, and just being a supportive grandma that like to spoil her grandkids.

My aunt who is 65 she always spoiled her two sons, and now they grown up, the youngest (age 36) asked my aunt for twenty thousand US dollars for him to invest a new business, he doesn't even think about her old mother need money to feel secure as she is aging and need medical in the future. And they both left their own sons (with their ex wives) for my aunt to take care and live with her but they both move on their new lives with their new girlfriends. This is the consequence of how my aunt spoiled her sons and never let them learn responsibilities. Hope you will be able to let go.