As long as it isn't spewing out any blue of white smoke out the tailpipe and everything sounds and feels good it should be running for years to come

Just test drive it, give it a propper tuneup if you do buy the car and all will be well.
Although it's a lot harder, even 4A-GE's can break. So it will always be a risk in buying a car this old with a unknown history.
But other than the usual things that can happen to an engine if it hasn't had propper maintanance (Sludge, running hot, raffeled timing belt, etc, etc) there are no real problems with the 4A-GE's themselfs.
But do check if it doens't have the well known problem of '5th gear pop-out'
The gearboxes sometimes have the tendency to pop-out of 5th gear when they were abused in the past or from old age.