Pilot,
If we were talking about a vinly top I wouldn't bother taking any maitnenace precautions. Vinly is incredibly durable against sun, rain and dust.
But these canvass tops are a different story. If you leave your car outside when you're at work I would definitely cover it with one of the $40 top covers I use.
It only takes one minute to put on and protects the interior from fading. I also find it cuts down on interior cleaning significantly. Not to mention cleaner glass.
Dust is the big enemy, its the big culprit in causing tears where the top meets the bows. A weekly stiff stream of water will do you allot of good. No Soap though..
I'm on my second top cover after only one winter. You should see it, the threads were coming apart and the sheen from the cover is completely gone.
But actually, I think the summer is harder on the top than winter due to fewer rain fall and the accumulation of dust.
and Of course you should be using Raggtopp which will protect the exposed portion when the top is down. Personally I wouldn't leave the top down for more than an hour uless you have applied 303 to every inch of your interior.
I've seen allot of convertibles that look imaculate on the outside but the leather and dash looks about 10 years older than the car itself, which just ruins the whole experience, especially on a Porsche.
as far as my interior, I use 1Z Einzett Vinly and Rubber protectant on the dash (and tires) every two weeks and 1Z Einzett Cockpit premium every week. Klasse VLRP is good for the black plastic, makes it look new. I keep those little Meguiars and Black Magic brushes handy for getting in the vents an all the other dash crevices. Keeping a convertible looking new is easy if you do it briefly and frequently.
