Miles and condition

[drift freaq]

I would say that yes a NA engine can have high mileage and run great and last a long time . When you put an engine under boost though you are adding a lot more stress to the parts especially if the engine was not built specifically for boost.
Now granted a low mileage KA can handle boost well but just like your body as it grows older it may still perform fine but it gets wear and tear on it . This is almost impossible to prevent in fact its pretty much a given.
It is pretty much taking a risk putting an older engine underboost due to normal wear and tear that can weaken stuff that if not boosted would work fine . Boost raises compression by packing a denser air fuel mixture thereby creating more power. MOre stress period.