Like what Winged mentioned, I go by the feel of the paint, if it feels smooth then it's all good but if it's rough then it needs doing.
Also if anyone uses the Meguires Quickwax, when you apply the stuff it should bead and if it doesn't spread quickly and shine up then it's time for a re-wax.
Motor May 2001 Quote: "Believe it or not, there are actually a bunch of weirdos out there who reckon a six cylinder is the dux gutz. Bugger it: I'm one of them" :s5
AUII Late Ed XR6 HP T5 Venom- Full Tickford Body Kit, 17in Wheels, Herrod Bi-plane Spoiler, Momo Steer/Gear, T-Series Interior Options, Premium Stereo and a very light-tuned 4.0L I6
(FPV-Tickford Club of NSW Member and Co-Founding Member of 3FB Inc, Ford Forums Food Bandits)