A rebuilt engine for a vehicle if properly rebuilt should last just as long as a brand new engine should.
I've rebuilt an engine in old truck and the rebuilt motor in the truck so far has 150,000 miles on it since I rebuilt it and it's still going very strong and should last even longer.
I've seen some rebuilt engines last 300,000 miles and sometimes longer.
When you completely rebuild an engine the engine has new parts put in it to rebuild it to like new condition so if you properly rebuild the motor and properly hone the cylinders and do everything right the engine should run like new and even use less gasoline and pollute less.
The rebuilt engine should be more efficient and very reliable just like a new engine.