I've been in Vegas for something like three weeks now. I never play on checkout day, and I almost never play on check in day.
First resort, end bill was about five hunny, and that was just tips and spa retail (spa services covered 100%). And I won money.
Second resort, the total bill was barely over a hundred dollars. Again, all spa services were covered, only thing left was spa retail and tips. We ate only take-out in-suite food that leg of the trip (pretty much ate only take-out at the first resort too), so restaurant tips were almost nothing. And I won at that resort too.
There is no need to knock yourself out playing on check in or check out days. You'll generally be tired on check in days, so why give them any edge? Check out days you're under time constraints which is also a bad scenario under which to play.
So no you do not need to play on check in or check out days to be fully comp'ed. I probably average three or four hours a day for the days I play NOT for every night of the stay, and I still get fully comp'ed. At the first resort my average bet was probably something like a thousand, at the second more like seven hundred. Table games only.