The call centre I worked had a few shifts available as 4x10 hours for 40 hours (or sometimes a bit less depending on what the phone company we did the work for wanted). Most who got them didn't want to let them go thought they were a drag.
The good ones would get there 10 - 15 mins before shift start to get logged in, you'd have 10 hours on the phones, 15min break, 45 min lunch, 15min break so it was pretty much 11 hours in the place.
And not sure why doing 4 x 10 would mean less vacation time than 5 x 8. You've clocked up the same number of hours.
Guess you'd also have be working in an environment were you it could be done but I guess as 9 - 5 opening hours are dying out it's less of an issue.