Many thanks, everyone! Geez; 10 years? That's longer than my central A/C lasted before I had to replace it. I hadn't even thought in those terms, especially after my neighbor's 2-month experience.
I'd never considered the run-it-periodically thing. Kinda like a car you're storing for a while? Keep the coolant circulating? My neighbor already took his Tosot Chinese model to the recycler, but he did mention that he could never
see any evidence that the coolant had
actually leaked out. I wonder if the coolant was still in there but just couldn't circulate after being shut off for 5 months. He said their customer service gave him no troubleshooting options, just "ship it back" as the only choice.
And LG and Arctic Air really weren't on the radar. Glad I asked.
LimaCharlie3: Manual controls would be just fine for us since the unit will only be about three steps away from the desk/bench. And looking at
this article from Consumer Reports, for our baked-in-the-sun building we figured 5,000 BTU was what we'd be looking for (and I lied earlier: it isn't 10x12, it's 10x15; not a big deal for the A/C, doesn't seem, but no wonder it
felt a little bigger than 120 sq ft). Even though a unit that size isn't going to be very heavy, I'm not sure I trust the structural integrity of the window where it's gonna go, so am planning on using one of those external braces to help support it against the exterior wall.
And RPBrown, I hadn't thought of looking at a heat pump, either. We'd just assumed we'd use ceramic space heaters in the winter (we bought an extra one of those with the intent of letting it keep the garage from freezing in February's icepocalypse, but then, of course, no electricity for days). The little building actually isn't bad in the
typical Houston winter; it's sealed pretty well. But the aluminum shell simply bakes in the summer sun. If it's a cloudless August day, it's a sauna in there. Going to do some research on it.