if you enjoy it, then who's to stop you? like most people have stated its open to all ages, if you enjoy it then play it, if you don't then its best to walk away. I do feel runescape is going downhill rapidly over the past 6 months or so.
I started playing RS when I was about 11 years old and quit when I was 16. I just came back to RS this past summer at 20 years of age, and just turned 21 a couple of weeks ago.
So no, I don't think you are too old to play RS As long as you have time to fit it into your schedule and it doesn't get in the way of your other priorities (school, work etc.) then I don't see the problem.
I don't think it has an age limit, though it seems that nowadays the average player is about 12 haha. I'm 18 and I still have a few friends that I player with.
If you enjoy doing something, an age shouldn't be the one stopping you. RS is probably one of the best ways for me to spend my time and I couldn't care less if it's meant for younger or older players.
Don't let age stop you if you're going to enjoy it. Jagex have stated many times they do not believe RuneScape is a childrens game. Being older probably allows you to play better, because you're wiser, have more knowledge and better literacy/understanding.
You're never too old to do anything you enjoy, but If you feel Runescape isn't for you any more at this time and point in your life, you can always take a break and come back to it latter if you wanted too, or you can just say fuck it and quit all together.
Well I started around when i was 13, I quit numerous times, But I'm 19 now and I play in moderation I'm not addicted, I just jump on now and then and do a little staking.