We have two grown sons. They've been to WDW (on us) virtually every year of their lives. But, we've been "weaning" them off this concept for about the last 7 or 8 years. We go once a year as a family, mom and dad go twice (Flower and Food & Wine Fests) without them.
As they get married and provide grandkids, we'll continue the once-a-year family trips, but we'll also do our adults-only trips as well.
We have found that WDW has grown as we have - providing all sorts of leisure, food, adult beverage, entertainment and just pure fun stuff that makes us totally "forget" we've left the kids behind. There are so many more Romantic things to do at WDW than most people expect, realize or uncover. We have made it our quest to discover them all......and then all over again.
We also sometimes "turn your question around". We get to be the "kids" bringing the parents to WDW! We've brought my in-laws down twice (they're both in their 80s), and they absolutely love seeing WDW through the eyes of their (fifty-ish) daughter and/or they're grand-kids!
We only wish we had joined
DVC earlier so we could afford to take 3 trips a year, treat the kids......and treat ourselves.