Personally, I think its great that you have put 6K miles on the bike and are able to do 50miles -- and especially that you feel good afterwards
As I walk up and down my street, I don't see many people who could do that. Or, if they did, they would have to push themselves so hard they would be recuperating in the ER afterwards.
Also, one of the posters here (I forget who -- I'm sorry) points out: "There is no such thing as 'too far' -- just not enough time"... (And I further apologize for screwing up the quote as well!)