I'm a long term employee of a large software company. When I had kids I asked to go down to 4 days so they wouldn't be in childcare for the whole week. Now the kids are all in school but I've kept the 4 day week as I'm much happier this way. A few years ago a colleague asked to go to 4 days (with no kids) and was rejected, so I doubt I'll ever give it up, otherwise I'll never get it back, and I don't know how I'd ever find another job that would support this style of work, so I guess it has worked in my employer's favour.