I usually try and do a little maintenance when camping, just five minutes or so, anywho i always put a little silicon spray on a cloth and wipe it over my zips, nothing worse than having a zip stick and end up damaging the stitching in the canvas.
I figure whilts the camper is set up its the best time to do any work on the camper.
This doesnt answer your question but may help you at in the future
Cheers
Darren.