Dwarf trees live shorter lives than fullsize. What about weeping trees?

Most weeping varieties have a shorter life as you suspect. Trees like weeping willow are quick to grow and quick to die. That is a common rule quick to grow quick to die. Some weepers are grafts so that may subject them to less tolerance in adverse conditions. Weeping mulberry is a graft and applies to this. There are some weepers such as weeping yaupon (illex vomitoria pendula that has a fairly long life however it grows moderate to slow.

It depends on the type of tree you are asking about. Most weeping trees should last as long as a standard tree under the same conditions. I am not sure of what sort of a fruit tree you are asking about. I cant think of any weeping fruit trees at the minute.

I was thinking of weeping mulberry for instance.