Thanks so much for your replies! I got the 4Runner back from the dealer, and no surprise here, everything checked out "normal". To answer someone's question, I typically keep it on LOW (temp) and recycled air (stays cooler- 115+ degrees outside). It doesn't seem to matter if the blower is on low, high, or anywhere in between.
So next I am going to have the regional technician guy who comes out once a month look at it. I already contacted Toyota's customer service after the 4th visit to get in the system, and that was their suggestion/next step (see the tech).
And when I had suggested, as one of you had to me, that maybe it could be some other system, ie electrical, the "mechanic" just said he didn't think so. I don't see why that's not in the realm of possibility. And I'm not really mechanically "inclined" in the least- just logical! And yes, picky, as someone pointed out
. And I should be for a $30 grand suv!
Thanks again, and keep the input coming b/c I plan on using it if needed later, and I'll post again any results from the tech so that it could help anyone else experiencing this.