Ever worsening a/c problem

I've had a problem with my A/C that has been getting worse for the last two or three years. I've asked the dealership to look into it 3 or 4 times, but either they never have, or they never found anything. Up until now the problem has been minor enough to ignore, but it's getting to the point where I can no longer ignore it. So I thought I'd explain what has been happening, and see if someone says, "I've seen that exact problem before, it's something detailed.

Started a few years ago. I noticed that much of the time if I had my A/C set on a low blower strength, it would barely blow at all, though it used to. At first it was if it were on spots one or two, it wouldn't really blow, but as soon as I moved it to 3, it would start blowing. Then it had to be four or five before it would start actually blowing ... though if it wasn't really needed, I'd just keep driving, then it would randomly decide to start blowing more powerfully.

Went out driving passengers today, and it's a hot Florida summer day, and the temperature was getting higher and higher, and I was cranking the A/C higher and higher, and it wasn't doing anything. I finally got it cranked up to max (7), and it still wasn't blowing. While the dash still claimed the inside of the cabin was 72 degrees, it was getting hotter and hotter inside. It got to the point that customers were starting to complain, and I finally had to stop accepting new calls.

By this time the A/C had been on max, but hadn't been blowing at all for maybe 40 or 50 minutes, and then it finally turned on and started blowing lots of air, and didn't give me any more problems for the rest of the day, but for an entire hour or two it hadn't been doing anything, when it should have been. Any fairly confident ideas of a possible problem?

Myself, I find myself beginning to wonder if maybe there's a thermostat somewhere that's somehow 'sticking' worse and worse and worse over time?

 

More than a day and this still hasn't even been approved to be shown to people. Obviously I am wasting my time here.