Well, I'm close to the type of person you were looking for a response from. Not over 30, but close to it. I'm 27 next month. But I am quite sure I NEVER want kids. Would have had a tubal years ago, but can't find a doc willing to do it for someone my age with no kids....
Anyway, I was on depo for about 6 years. Have been off it almost 3 now. I didn't have a lot of the horrible side effects that a lot of women get. I really liked not getting my period for so long. When I went off it, it came back right away, right on schedule.
However, I wouldn't recommend it. There are less drastic options out there to control your period. I was on Depo for a few years before they even knew about the bone loss thing. Haven't had a bone density scan, but I'm sure it's not gonna be good. My reasoning for this is that I've ALWAYS had good teeth - no dental issues at all. Since starting Depo, that started a slow, but consistant decline. Now I have SO many cavities & whatnot that I don't know what to do - my insurance won't cover all the work that I need done, etc.
I don't have any proof that the Depo caused the sudden change in all that, but I can't think of anything else that might have been the culprit. And bones & teeth are similar, so.....
Plus, once you start Depo - even if you have AWFUL side effects - you're stuck with it for 3 months. At least. From what I've heard/read stopping it sucks too - can take a long time for your body to get back to normal.
I would recommend trying something else first - you have lots of options. Talk to your doctor about it.
Especially being over 30, you don't want to do something to screw up your bones. You don't need to have osteoporosis at 40!
Just do plenty of research before you make a decision.
Hope that was at least somewhat helpful