Never too old to join a band, as long as you don't plan to go mental on stage or anything, you'll be golden.
You'll need to work out how much time you have or want to put towards practice/rehearsals/gigs and move forward from there. As long as you're open with yourself and band mates about time, you're be fine. If others want to rehearse all the time, and you don't - it's never going to work. Aim to find peeps similar to you, in terms of what you want to play, and time you all want to put into the band.
Finding others on the same wavelength isn't easy, but sometimes things just click.