5 days can be excellent QOL trips if they're built right. We're conditioned to place massive, near absolute, value on calendar days off. But that often doesn't tell the whole story. Some of the best QOL I've had were 5 days, both living in base and as a commuter. Low leg 5 day trips that are hyper-commutable on both ends and great layovers are far, far better than crap 5am report, 11pm release 4 days with short rests, more legs and constant plane changes. Better for commuters as well as in base pilots' QOL in many cases.

I do agree that 80% or more 4-5 days is very excessive. A healthy trip mix helps everyone.