I would like to keep my apple, peach, pear, cherry, etc. fruit trees to no more than ~12' tall and ~12' spread and get good quality fruit production. In GENERAL do dwarfs produce fruit for 10 years (Stark Bros said 10-20) reach about 12', S/Dwarf produce a good harvest for 15 years reaching 16' ,and full size trees produce for 25 years reaching about 25'?

If you prune a full size or S/D to the size of a dwarf tree will you still get the longer life of fruit production and can you get the same yields as a dwarf?

If the three tree sizes are from the same "mother" will they be equally disease resistant and the fruit have the same flavor if they are planted in the same environment?

Thanks. Just trying to figure out the pro's and con's of each.

S/D had better last longer than that. It took mine about 5 years before it produced anything. I don't remember exactly when it started putting out a lot but it was probably closer to the 15 year mark than not.

My niece has a S/D that is probably 30 years old. The trunk is rotting away and they pruned it horribly but it's still going.

Rootstock has a lot to do with disease resistance. They also have to do with precocity, fruit size and many other things that go into the final fruit.
So no, the three sizes will not be the same, although they may be very similar. It all depends on if the rootstock is suitable for the site.

This is just my opinion but I don't think the size you prune the tree to has anything to do with how long it lives and produces. Keeping it disease free and healthy equals longevity.

I noticed one of the peach trees labelled as dwarf does not have a visible graft on the trunk (like other dwarf peach trees or dwarf apples trees I have). Does this mean it may be full size (no grafted root)? And if not grafted, it is the same thing as just planting a peach pit and hoping the resulting tree will be as good as the parent?