Okay – a four-day week sounds tempting on the one hand, but on the other hand the place I'm working has a smaller-scale version of that arrangement whereby 8.75 hours Monday thru Thursday instead of 8 hours (lunch break not included) gives six additional days off per year plus a slightly earlier finish on Fridays, and personally that already often felt long enough, nevermind 10 hours plus x days. At least this autumn the working week has been reduced by two hours, so now it's only 8.25 hours + x. Because our working hours are somewhat flexible within reason, I might possibly get away with unofficially implementing that 4x10 model on my own, but 10 + x hour days really don't sound that tempting to me.