This is interesting. At my employer we see job hopping as a bad thing.
I think there's a unique perspective you get by seeing your 5+ year old code in production. I can kinda tell when someone only does short stints based on the way they talk about other people's code.
18-24 months generally seems to have been the sweet spot in terms of improving your income. Especially because the promise of equity after 4 years often means fuck all and you almost never see a promotion or a decent pay increase either for inflation or performance.
If an employer is going to ding you for taking advantage of the market then they better be offering enough above market to keep you around for longer.