RE: Three sets of tires... yeah, I've had 3 full sets for the last two cars I've owned. I'd obviously prefer only 2 sets, but I find there's a gap between the suitable conditions for winters and suitable (safe) conditions for summers, which is when I use the no-seasons. I typically run the no-seasons April-May, and again Oct-Nov/Dec, depending on the conditions.
While it is more expensive to run three sets of tires, I've found this gets me an additional year or two out of all three sets, while also making it generally safer to drive. It won't offset the initial outlay of cash (I think) but I'd rather be safe.