Hm every 2 months
i would like 7500miles from my standard V belts on a 68mm pulley. (its holding it for already 9000KM) but the belts slip every time at 5500RPM+
even when i use anti slip beltspray. without the spray its 5000-5200 RPM when just tightenned
the plus side is that i dont / am not able to mistread my charger :p
since it is my dayly/only car (not that i use it every day) i m gonna try shorter belts & a new steel pulley (this one is aluminium and worn in after 9000KM)
i hope this will help. im running a 140hp chip, the charger is done also 9K KM ago..