We all have to hang onto those good days!
My son brings up that kind of stuff from time to time - I just tell him that we're both going to live to a ripe, old age.
When he's fairly well and realizes that he's not functioning like other people, he'll tell me things like he wouldn't be able to live without me and that we might as well get a double coffin - or urn, since I don't plan to be buried.
I keep stressing to him that this new program he is in is designed to help him be able to live independently if that's what he wants, and that they will step in to help him if anything happens to him - since we don't have any family we could depend on to do that.
Him & his father love each other, but it's best if they only see each other for short periods and I don't think they could live together if I wasn't around. If there was a true crisis, his dad would be there and be great, but it wouldn't be good for everyday.