I've been back twice in nine years and that's more than enough. I'd rather save my travel money to go to more exciting places and places I haven't been to before.
That's my feeling, too. Flights are so cheap from the UK to Asia, Africa and the rest of Europe, so I decided to let my parents come to visit me and I'd do a lot of travelling. My parents would also prefer to visit the UK than have me visit them. For £1500, my husband and I could fly to the US, but for £800, we could go to Asia, so we obviously chose the latter. I'm an only child and since my parents were visiting me, I really didn't have a reason to go back besides visiting friends.
I arrived in the UK in May 2008, and the first time I was back in the US was in April 2011, so I spent three years away and actually didn't miss it at all. I think it's different if you have a lot of family there, though.