QUOTE(flotsam @ Jul 18 2008, 12:14 PM)

I've been using autoglym.
The wax is good, in that you leave it for 30~60mins before polishing off, so there's no rush. But I wash the car once a month and it seems to need re-applying the wax each time to get water beading.
Water beading is merely a function of surface tension rather than an absolute indication of any LSP being there or not.
Irrespective, monthly reapplying is better than winging it to see if you can do it once every other month.
But it's also worth remembering to remove all the wax 3-4 times a year anyhow, since carnauba degrades due to sun's rays, airborne contamination, bird bombs, industrial fallout, etc, etc.
So aged wax needs removed rather than continually layered upon.