Easy, book smaller accommodations so you can stay longer. An 8-day stay is a lot more amenable to flexibility than a 4 day stay.
We go for two weeks at a time. In that, we hit the parks about half the time. We only do a few all day park adventures. Most of the time we split our time between resort lounging (pool, sleeping in, long walks, dining, shopping) and park touring. With Annual Passes, we can also pop into a nearby park for just one thing (fireworks, a ride, to buy something, to eat) guilt-free.
Some of our favorite non-park things to do include:
Fantasia golf
DTD shopping
Afternoon Tea at Grand Floridian (followed by a stroll along World Showcase Lagoon to the Polynesian)
Breakfast at Chef Mickeys with shopping on the Concourse
Breakfast at Cape May or lunch on the Boardwalk
Lounging at AKL with dinner at Boma's
Long walks around SSR with our morning hot coffee/chocolate/tea
Soaking in the SSR hot tub and zero entry pool
Ferry rides to OKW and POR
A night out at Pleasure Island
On our ToDo lists include Fort Wilderness for the petting zoo, WinterLand/Summerland golf, DisneyQuest, and some of those tours. (We're divided on whether they destroy the magic.)
If you can allow each other to split up for a few hours, you can broaden your adventures too. We have been know to split up and do different things with a meeting place later. You can get up and go ride Tower of Terror 3 times, while she sleeps in and has a nice bubble bath. Then meet up for lunch at Brown Derby.