Not just 18 yo drivers can have a trash in a GTR. A lot of GTR's are brought to the track for some fun.
An 18 yr old car that was built to be trashed and has been trashed is likely to need an engine rebuild sooner or later. If you just plan on raising the boost a bit and keep things fairly standard, theres nothing stopping that stock engine from lasting you another few years as long as it was healthy to begin with and you service it regularly.
That said, if I was to buy a 32gtr again, I would look for one with a fresh rebuild by a reputable workshop, just to be safe.