I don't think there is a perfect time, maybe a perfect opponent, see who are the most aggressive players and give preference
I think you hit it right on the head, don't look at the situation, look at your opponents' tendencies, if they're going to lead into you. That said, usually flopped monsters (like Quads) are likely only going to get you one street of value post-flop against most good players. But, of course, there will be that spewy player who will bluff into you, which is great for you.
I had a situation today on ACR where an opponent, with position on me, I think because of my own aggressive play (was playing PLO, not Hold'em), was 3 betting me a fair bit (I think I had about 40-50 hands against this specific opponent). I wasn't really slow playing against them, but I did come across a situation that was the perfect storm to do it (I had just won a decent sized pot an orbit or two earlier and I think they might have been steaming a bit).
Anyhow, I was UTG and raised pot (3.5x), and, as expected villain 3 bets pot (12bbs). Everyone else folded, and I called. This hand heads-up against someone 3 betting a fair bit plays well, even out of position. If the flop hits me hard, I can get his entire stack. If I whiff, I check-fold.
Flop was such that it smashed my range REALLY hard. So, I wanted to take advantage of his aggressiveness, so I decide to slow play here. I checked, and as expected, they potted the full 25.5bbs. I decide to play the hand fast, as there is a flush draw on board AND re-draws for higher straights, and they VERY well could have AAxx with the nut flush draw, as people in PLO will play their flush draws SUPER fast. I shoved for his last 60bb effective, and he folded. I won a 72bb pot.
He left the table about 2-3 hands later (maybe was steaming, I don't know, but it was nice to pick him off).
But this is where you gauge your opponent and what they are capable of and use their aggressiveness against them. Conversely, you can do the opposite and use someone's passiveness against them too.
When you flop 4 of a kinds and the chances of being outdrawn are very slim. At micro stakes I highly recommend not to slow play hands. Donks and fish will pay you regardless so make them pay as much as possible.
Yes, there will be some players that are just never going to fold even 1 pair on a board, no matter the board texture.