I think most of your question have already been answered. I'll throw my perspective in as well. I've been a volunteer in Oklahoma for almost 24 years and was Chief for 5 years(I'm actually retired now but still help out some).
First, I think I would ask what calls to they run most often. How many calls to they make? What training do they provide and when? Also does it cost to you to train? If you have to take two weeks vacation to attend Firefighter I and also pay for the class that might not be something you want to do. However if the class is paid for and is offered in the evenings/weekends you might be good to go. Just be aware it's not only a time commitment to the department it's a time commitment to training. My oldest son also volunteers for my department, his first year as a rookie he attended well over 200 hours of training. That was anything from structural firefighting, to wildland, to EMR. It was all done on evenings and weekends at not cost.
As long are you are in good physical condition your age shouldn't be a problem, however structure fires are a young mans game. Wearing 60lb of heavy gear, crawling around in 600+ degrees is not what I feel I can do much of anymore at 48 years old. That's not to say there isn't something your can do at a structure fire, there are lots of jobs other than being a hose dragger. Now wildland, I can walk some of the pups in the ground cutting fire line, it's a different set of physical requirements.
Some other things to ask yourself. How well do you handle blood, puke, people suffering, KIDS suffering, and there isn't much you can do about it? It's a sobering thought but it's something you may have to do. Even if the department doesn't run medical calls
All that being said, it can be a rewarding job and knowing you are actively doing something to help your community and others is a great feeling.