Cheap PSU will have cheap components aka cap ayam.. Overtime these components in this cheap PSU will deteriorate .. cap ayam capacitors used that was responsible to smooth voltage/current rippling will go beyond tolerance level.. which may cause system stability issues or worse causing permanent damage to your PC components.

Depends on "stress level" ... high stress level (High end GPU/CPU) may accelerates deterioration. if your PC doesn't stress as much like an office PC... well it may keep up.