I am group riding for the first time this year, keeping up with the "faster folks" is out of reach for me at this juncture. I am younger (49 years old) but smoked cigarettes for years (kicked the habit Jan. 2010). I am group riding to get used to riding with other people because in September I'm riding the MSbikeride a few thousand people. Yesterday I went for the longest ride for me so far, 40 miles. I rode solo and really enjoyed it! Not to say I don't like riding with other people, I do. It's just nice if the group can stay as a group. As stated above - riding a bike is suppose to be fun!
Do what feels right for you! Enjoy yourself. :-)