The biggest use is for DHS/Epcot. We go during Christmas week, so big attractions usually have 2-hour-plus waits.
With DHS being our favorite park ride-wise and having tiered FP+ selections, we usually break it up.
On one day, we’ll spend the morning at EPCOT exploring the World Showcase and eating around the world. Then we’ll take a break in the afternoon and head over to DHS for TSMM FP+, Tower of Terror FP+, Star Tours FP+ and Fantasmic. Another day we’ll do DHS in the morning, with a FP+ for Rock ‘n’ Roller Coaster, Tower of Terror, and Frozen Musical. We take a break in the afternoon, then head to Epcot for Illuminations.
We stay at BC, which makes this really efficient and we normally stay around 8-9 days.