As much as I love staying on site, I've loved our off site trips as well! My favorite one was me and the kids for 15 nights off site (we did back to back Interval getaways, so started at Marriott's Grande Vista, then moved to Sabal Palms, which was wonderfully amazing!).
Longer trip meant so much down time, enjoying the pool, I used the fitness room every morning, we used the kitchen and gas grill right outside our door (literally). Full size washer and dryer was great! Lots and lots of space! We did a little exploring outside of Disney, and only ate one sit down meal that whole time (at a Macaroni Grill in Kissimmee, which was a great meal too).
It cost so little, as it was the last two weeks of August. No lines anywhere. Rental car was about $230 for the whole darned time.
It is what you make it. For a larger family, off site can be super fun! There were only 3 of us, so it was easier to wrangle the kids up to get moving (not an easy task for my son, LOL). We never got going until noon at the earliest, but I was pretty relaxed about it, and made breakfast many days. We used Marriott points for Marriott gift cards (a platinum perk that isn't available any longer), so our tickets were free. Lodging the whole time was well under $1,000. We grocery shopped so spent no more on food there than we would have at home. Flights from BWI were super cheap, I'm sure it was less than $600 total. Staying on site, even in one room at a value resort, would have cost more, and we wouldn't have had the huge condo with our own kitchen and washer/dryer.
I'd look into it certainly!