Hey, simonmunro -- we do the same thing! We eat mostly counter service (6 days? Pah! Try 3 weeks!), and occasionally eat at the sit down places around 3 pm. Why 3 pm? Because we NEVER have to make PSs anywhere (no matter how popular the place), and the places are almost empty. This has the added advantage of the waitstaff being unhurried. At 3 pm they could are less if you order 3 desserts or 3 entrees. They're grateful they're getting any business at all. We very frequently order three small things, or an entree and two appetizers, or even two appetizers and a dessert. Who cares at 3 pm? Nobody!!!
We've done this at all different kinds of restaurants, from the lowliest to the most upscale. There are a few restaurants that serve only from dinner onwards, so you will have to make PSs, and they can be snotty about ordering small portions. But my experience with upscale WDW restaurants (Flying Fish, Maya Grill, Artist Point, etc.) is that they are not generally up to the level of upscale restaurants I frequent in the outside world. If I'm going to pay that kind of money, I want a meal that justifies the price, and I just haven't gotten it from the WDW restaurants. I feel (just my opinion after a LOT of eating around) that you get the most bang for your buck at WDW counter service.