How long is a piece of string?
Depending on age, use, condition, servicing, fuel - and anything else you can think of - will depend on how long it will last.
Will it last forever? Highly unlikely. Have seen people with only 450rwhp end up having to rebuild after 2-3 years of circuit racing as the motors just started to breathe heavy. So not blown, and not tune related, just age and use.
If you can't/don't want to rebuild, then don't chase the power. It's as simple as that really.