Reliability is in the eye of the beholder.
Any power increase is going to lower the life of the engine.
I don't know the exact numbers but for example if a stock 45bhp NSR lasts about 20'000kms before requiring a rebuild, a worked 60bhp might do 10'000-15'000kms before requiring a rebuild. Some of us including me consider that an acceptable drop in engine life for the extra power gained.