My son (and the kids of my dvc friends) grew up going to WDW frequently, with multiple trips every year. For a couple years in the early teens my son was rather ho-hum about it, but that's no big deal. He was old enough that we could separate - he'd spend 10-12 hours inside DisneyQuest and I'd do other stuff. A friend of mine who's son is now 16 flat out refuses to go on her WDW trips any more. She left him home last time (as she should - he's old enough, and why pay for a grump <g> who eats like a horse). Most likely he'll come around - my son loves it again now that he's 21 and has a girlfriend he can impress with his Disney knowledge and *my* dvc studios they don't have to pay for ;-)
As for me - I don't tire of WDW, but I sometimes tire of the whole rush to the parks to avoid the crowds thing. I don't spend much time in the parks, but I still love my trips. Many years ago, I'd be in the parks from opening until closing, but not anymore! I like the resorts and relaxation far more than any attraction in the theme parks. DVC works very well for me as a nice place to escape the pressures of real life. My last trip included no parks at all - just the resort, dining out, laying by the pool, and Comedy Warehouse at night.