I am really on both ends of the spectrum but with little middle ground on this.
When I run, I do a new campaign setting each time. I have more ideas for campaign settings then I will ever have time to run (my average campaign is 4+ years), and I try to plan around a campaign around the things that make that setting unique, that wouldn't work or wouldn't be as effective in other settings.
That said, my formative years of playing were with a DM who ran well over a dozen campaigns in the same world, many of them concurrently with different groups (and sometimes overlap of players). It made the world so rich and dynamic - there were things going on outside the scope of what the party were doing, often world-changing. We would do occasional crossovers and be like "Oh, we're heard so much about Arlitha!", or becoming patrons. Heck, we had one powerful adventuring company that effectively brought in new parties under their charter to go do things we needed more manpower for. And since this was AD&D 2nd, we would often have a load of spare magic to give them. "Here, take this +1 trident, this ring of water breathing, and this chainmail +1, we don't need them".