I try to PO everything I want, and most importantly put them on installments. It helps me keep track of it all and pay them off slowly. But you are right in that I take my time with it. With most of them anyhow. Like I've said, I have a general list of all my wants. I rework it every now and then, but it's my blueprint, so to speak. Based on announced movies and the such, I also have a map of sorts for each year, and I know more or less what I need. Then I see how high the number goes, when the release date is projected to be (ie a movie from Q1 will get POs in Q2 and release the next year's Q4 or later, while a movie that releases Q4 of a year more or less jumps 2 years ahead for release; you get the point), if I'll have another chance to get any of these figures, and so on. So there is planning that goes down.
Now, there are characters/figures/costumes I'll PO Day 1 because they're absolute locks. But everything else depends. I give them a month at least, to see what else gets announced, to gauge how I feel, and so on. Some months back I was tempted to PO Infinity Ultron because I figured he'd double for an Annihilation Ultron. Then I realised it wasn't all that close to the source, he's a character that's in my mid tiers, it's too expensive and 2022 would be packed, so I dropped him and... that was it. I stopped thinking about it. Really, a lot of this comes down to FOMO and compeltionism. Once you distance yourself from it for a bit and see the bigger picture, you're able to have more restraint.
I've got a Mando Luke, TDKR Batman (waiting for the 3.0 Joker...) from HT, the Iconiq Bateman, that new AUGTOYS Paul I took a gamble on and then BCS' Tommy Shelby & the 12th Doc (plus the Dam Vito, but I'm done paying him off in 2 months or so). The last two I doubt I'll see before 2024, and it's up in the air for the non-HT ones.
I started with Tobey, Ock & Goblin from NWH. Now I'm down to Tobey & Goblin. I wanted a SpOck and a 2099, but I'll probably scrap the former and only get the latter if we get a proper Batman Beyond too. I try to cut as much as I can because it's all becoming more and more hectic and I want to at least get the essential ones. I might skip, say Battinson and MK and hold out for versions down the line, if through Kenobi we get re-releases of ROTS Obi-Wan & Anakin, or if DS2 gives us many of the rumoured cameos. It's too much for me to speculate, so I just go off the general plan and I do the math.