Not counting work issued Macs:
1994: Macintosh Performa 630CD
1997: Power Macintosh 7500
2000: PowerBook G3 FireWire (Pismo)
2003: Apple iBook G4 12”
2006: MacBook (white)
2009: Mac Mini Server (+ 2010: iPad 1)
2010: MacBook Air 11”
2019: MacBook Pro 13” (2 TB-ports)
2020: MacBook Air 13” M1
So for many years I upgraded every 3 years.
Then i 2009, I got a Mac Mini server, hooked up to the TV, and the - then new - original iPad. Thinking I could use the iPad as a laptop replacement and have most of my "stuff" (mainly photos and music) on the Server. I also had the - then aging - MacBook at hand...
Now, it soon became clear that the iPad wasn't really a laptop replacement (for my use pattern, and still isn't), so when my white plastic MacBook died the following year, I got an 11" MacBook Air, which lasted close to 10 years. That was a very capable little machine, and I still kind of miss it. It's probably my all time favourite Mac.
The machine that replaced it, the last "baby" 13" intel MacBook pro, with touch bar, on the other hand, is my least favourite Mac, ever**. Heat, sound, that frelling touch bar interfering all. the. time. So - when the M-chips was introduced the year after, I did something I've never done before: I sold my Mac.
Then I got a M1 MacBook Air 13", and even if I've been tempted by some newer Macs, like the M3 15" Air and new M3 14" "baby" Pro (and even a M3pro 14" Pro), I have persevered. The little M1 13" Air is awesome, and might - if I don't get tempted to upgrade later - eventually match the 11" Air, maybe not in longevity, but at least in my esteem.
** Now, the 2019 MacBook Pro have a strong contender as "the worst Mac ever" in the 2015 12-inch MacBook, that I got at work. Although very nice to look at, that 12" MacBook was just an awful, stuttering mess to work on. I actually preferred bringing my - then 5, 6 year old - 11" Air to work. That was better.