If you're in a place with people you like, with sane management, and OK or better pay, do not be in a hurry to move to the next job. Positions with those ingredients are not real easy to find, and it stinks to be in a job without one or more of those.
On the flip side, if you're in a job that has toxic people, insane management, or lousy pay, don't stay because of inertia or laziness or a hope that it might get better eventually. Start looking.
Specifically about ageism: I have not seen it. I'm 58. What I have seen, though, is that I'm very expensive. I have 35 years of experience, and I expect to be paid like it. If someone want to pay me like I have 5 years of experience, that's not ageism, that's being cheap. If someone doesn't see the value in 35 years of experience compared to five years, fine, I'll work somewhere else.
For me to get away with this, I have to actually be more valuable than someone with 5 years of experience. I'm in embedded software, and it's easier for me to do so in that area than in, say, web programming, partly because the underlying stack changes more slowly in embedded. But also, I've had to keep growing in my ability to deliver what my employer wants in a timely fashion. I don't make as many design mistakes as I did before. I don't write as many bugs. I don't start down as many wrong paths. I don't work insane hours, but I still get more actually done and working.
If you can deliver more value per time, then you're worth more money. Do that and you won't have to worry about ageism.