I think, like most things, this is dependent on circumstances. Planned weekend work (downtime needed, pre-planned release, or timing with external factors) isn'

I think, like most things, this is dependent on circumstances. Planned weekend work (downtime needed, pre-planned release, or timing with external factors) isn't always a failure. Separate but related, an engineering team that is able to coordinate aggressive cycles on a regular basis, with built-in time to recover, is probably more productive over the long term than one that can't.