I've had many dreams where I die, but I never considered them "predictions". I can't even count the number of death dreams I've had, and I think they are relatively normal for people to have because it is our brain's way of processing one's own fatality.
For some reason when I was younger I always thought I would live to be really old, like in my 80s. As I've gotten older, sometimes I wonder if I'll live to see my 40s or 50s.
I'm 22 now and I never thought I would die in my 20s or 30s, though, I always assumed I would at least make it to middle aged.
I think my perception of my lifespan has decreased is because I am more acutely aware of things like cancer affecting those in their mid-life stages. I am also more mature and more aware of things like accidents or other diseases.

But no I don't think these dreams you're having are actual predictions. If you and the other poster are depressed about living past a certain age, I think that means you aren't living the life you want to live and you think death is a better alternative. Life can be very hard, but trying to make it better each day is the path we're all on. Death comes soon enough for all of us.