38, and it's pretty much the only thing I'm any good at. I work about 30 hours per week at the office, and do the rest at home or in the weekend. Some weeks that means I work only 30 hours, other weeks it can be 80+ hours. There's a huge amount of flexibility in this, which makes work-life balance a non-issue. Apart from the occasional pull-request, bug report, or comments on HN and Stack Overflow, there's not a lot of contributions I have the opportunity to do, but that has more to do with personal circumstances than with work or age.