I'm 40, the proud owner of 3 arcade cabs, and continue to put a great deal of time and effort (and money) into the hobby. Outside of DK, I also play a lot of Street Fighter online. That's where I feel my age the most. Some days, I'm playing my best and know that I'm keeping up with the young bucks. Other days, there's a clear disadvantage from being older, tired at the end of a long work day and after putting the kids to bed then trying to squeeze in some "relaxation" time, compared to the guy on the other end of the internet connection who could have very well rolled out of bed at 11:00 a.m., put in a few hours at his schooling or part time job, and otherwise have little to know responsibility or major energy drains.
That rant aside, I too grew up gaming (see my blog), everything from arcade to Atari 2600 and Vic 20, to start with, and I have no intentions of giving it up. Heck, I downloaded Metal Gear Solid V Ground Zeroes this morning because it is free for xbox live gold members, and I haven't played a MGS since the original release on Playstation (1), and I'm having a great time with it.