This nails it on the head for me.
I rarely spend more than a few seconds before providing an answer on an item, but sometimes I think I “know” the item and spend more time trying to dredge it up (lots of research shows this is helpful).
Of course, sometimes I then dredge up an entirely incorrect answer, which doesn’t help at all!
So it’s a judgment call, but personally, I think it’s almost never worthwhile to spend more than an agonizing minute or two trying to recall an answer. Even if you get it right eventually, an “extra” few reviews from answering incorrectly won’t hurt your long-term retention.
Remember that only way the SRS knows you find something difficult is if you answer incorrectly! You’re paying for a service to show you items you find difficult more frequently — you should never feel bad about providing a wrong answer.
My go-to “I give up” answer, by the way, is “ke” or “け”: quick to type, never matches meanings, almost never matches readings, and is almost conversational (kind of like “que?” in Spanish, kinda like “huh?” in Japanese).
Lastly, if you’ll forgive me plugging my own script, you may be interested in my GanbarOmeter user script. The difficulty gauge uses a slightly more sophisticated algorithm than just “keep 100 items or less in the Apprentice stage”. It also keeps track of the number Kanji in the first two stages as well as the number of misses in recent reviews, suggesting you slow down on lessons if either gets too high.