Hey Steve... The Ford tops have a tendency to like to crack at the bend points. On two cars, I have been through three tops. The one I have now is the first one I have been able to have on the car from the beginning, and it's doing great.
The color of your top is going to make a difference on how much maintenance you are going to have to go through.
With my tan top, it was easy. Wash it with gentle soap and water and a scrub brush. It didn't show the dirt.
With my white top, I have scrubbed, cussed, cajoled, wrestled, degreased, soft scrubbed, bleached and finally after the urging of the guys in the group used Simple Green. It seems to work as well as anything. The doggone thing will stay white.
As for vinyl treatments, that's a double edged sword. On one side they are telling you that it will 'protect' the top, on the other, anything with Silicone will cause the vinyl to dry out and then yellow severely. In the case of Armorall, it will be even worse, as it builds up like varnish. The top has (I'm sure you have noticed) a little grain in the fabric, any slick-em stuff you put on there will get down into those crevaces and collect dirt.
I park Shug in the garage sometimes for up to a month at a time with the top down (cover on) but when I do put the top up after that I let it stretch up gently, kind of like when you do warm ups before exercising.
The worst thing I have found, by way of personal experience, for your top, is to raise and lower it in very cold weather. It becomes brittle from the cold, and will accelerate wear. Like a big Hunk candy bar, in the sunshine, it's nice and pliable, stick it in the freezer, and it shatters into little pieces when you bend it...
Hope this was of some sort of help.
Kate
98 Cobra Drop Top