Before we bought DVC, we would visit once a year off-site. We actually thought that staying on-site was too expensive and not worth it.
A few years ago, we stayed at POFQ (during a BAD hurricane, BTW), because WDW was offering a special. It may sound cheesy, but you really are part of the magic 24 hours a day when staying on-site. We were so impressed with, not only the outstanding service we got when it was sunny, but the phenominal service (and quality of construction) during the hurricane.
We were hooked.
We now go 3-4X a year. Our vacation habits have changed since we go more frequently. No more "commando" - we get to relax, since we've pretty much seen all the rides. We'll take half-day trips to one of the resorts, eat lunch at a different restaurant, grab a cocktail at another, grab appitizers at another, dinner at another, walk the grounds, etc.
Before, it was all about the parks and the rides. Now, it's about the experience. Since we know we'll be back in a few months, we don't care if we miss something. This frees up a lot of time. Now, we do the tours, maybe go to the pool (which we NEVER did before), explore. And, we get to meet and talk to a lot of CM's. You'd be surprised how many remember you!
One of the things we do to keep the trips fresh is each trip will have a "theme." For example, one trip was a "Hidden Mickey" trip. Our goal was to find and photograph as many Hidden Mickey's as possible. Another trip was a "Pressed Penny" trip. Our last trip was a "DVC Stand" trip. We got our pictures in front of all the DVC stands we could find (at all the parks, DTD, and at the resorts). That was a neat way to explore WDW - and it offered a new perspective. You can make a trip where your goal is to get your pictures with all the characters. You can make a trip where your goal is to get your picture with a CM from each resort/park. So many different ideas.
Plus, WDW always has something going on to keep things interesting. Our next trip is a Food & Wine trip. We've actually coordinated with family and friends to all go down together. Or, someone on the DIS is always arranging a DIS meet at the parks!
Other great events to try are MNNSHP,
MVMCP, Flower & Garden Show, Soap Opera Weekend at MGM, etc, etc, etc. We're going in December for the first time to see how WDW decorates for Christmas. That should be cool.
Another great thing to do to keep WDW fresh, especially if you have extra points, is bring along someone who's never been there before. Offer to bring down a niece or nephew for a trip. If your relatives children have never been to WDW before, watching it through their eyes is like being there for the first time all over again!
To be honest, I don't know WHAT I'm going to do when my DVC runs out in 2042. DVC is one of the best decisions we've ever made!