"You will end up scoring a lot more points if you devote the same time and effort into increasing your proficiency at Rook and pawn endings, which occur in nearly half of all endgames."
It only took me 15 minutes, hardly a big waste.
Yeah but will you remember it several yrs later? I've had to take several "refresher" lessons over the years even though I know all the basics (you can only mate in or next to the corner the Bishop controls, the King and Kt cover the squares the Bishop can't, etc etc)
Now I think I finally have it down and maybe Estragon was right after all, but not in your case if you can really do the Mate In 34 in 5-10 minutes OTB no matter how long ago you studied this.
AND, K+Q vs K+R is way harder IMHO than this ending I've studied it several times and still don't think I "get it" and it's also rare, which is fortunate because the one time (eons ago) I had the K+Q vs K+R I couldn't win!
I have been playing chess 25 years. It has happenend to me exactly once. In a live game. And I had just been studying them, too. Unfortunatly, I only had a few seconds on my clock, and had to settle for a draw.