Let's see, I first went down when the park opened and I was 10 and I've been down 33 times, so it looks like my average is every 16 months.
When I was a kid and we had a motorhome, my parents would take us down there about three times a year (every Thanksgiving, Christmas, and Spring Break).
When I was in college and in my 20s and 30s, I really wasn't that keen on Disney, but would go down occasionally for a few days to join extended family (my brother and his family and my parents would do longer trips - like two weeks and we'd maybe go down for four nights / three days). Our major vacation interest then for me and DH was skiing.
When DS came along we did do two different full week vacations down in Orlando too one when he was six and one when he was 12. And DH has had several conventions at the Contemporary that we went down for too. DH, though, doesn't care too much for Disney or theme parks, so it was never a major vacation focus.
Then when DS was in Junior High and now HS (late 40s / early 50s for me), I got the Disney bug, and I did a few mini trips for maybe three nights / two days (just the two of us -- me and DS, sometimes meeting other relatives.) It is just such a fun thing to do with your kid. Our main family vacations are other places that all of us including DH like.
With DS being a senior in HS now and with his many vacation interests, I didn't know if I'd ever be going back to Disney/Orlando again (our last trip was in 2011), but OMG, we are doing another mini trip a week from Friday - three nights / two days. My nephew is in the Disney college program and DS and I decided to go down and visit him when DS had a Monday off from school. So we fly down Oct. 19th and this will be trip #34. I guess all someone has to do is twist my little pinky, and I'm down there. lol