I will pipe up and suggest that, while the magic doesn't fade, it does change quite a bit. As others have mentioned, the commando attitude and the need to "see everything" and "not waste a second" go away after you realize that you'll be back again, and again, and again..... IMHO, DVC helps us balance out the "vacation" vs "Disney" in the phrase 'Disney vacation": we actually get to relax a bit, have a cuppa on the balcony in the morning, read by the pool, have a quite walk around, and so on.
Regarding the parks, we have noticed that we can't do EVERY attraction EVERY trip - even if we tried, we wouldn't want to; we have dubbed some rides / shows / parades as 'every other trip' activities. Still, there's so much to do at WDW we never get bored.
But a trip to WDW & DVC is like Christmas or New Years - no matter how many you've done, you always look forward to the next one!