I feel that more depends on what army you're playing. I mean, everyone has the 'Codex tax' where you have to keep buying new Codexes and rule supplements. Unless you decide to just take one of the free alternatives that exist. But other than that, it's really faction dependent. A bunch of armies basically keep the same line of models for multiple editions before they see a new datasheet.
Though I gotta say, it helps if you just never sell your used stuff. Eventually you hit a point where unless it's a completely new unit that's never been in your Codex before, you'll likely already have it. And with how bad the second hand market prices are for selling, I've never found it worth it, particularly due to my memories of my models.