It is expected that in the last 1-2 months we're not just working 40hrs/5 days but probably 60,70, even 80hrs a week and likely 6 day weeks (the last project was 7 day weeks and I worked 71 days in a row without a day off). I'm not proud of this in the slightest and indeed will be refusing to do this again.
But - my situation isn't unique or even uncommon in many tech jobs that involve delivering projects to a (small) pool of paying clients. Our profit margins are also slim - there is no way my company is going to hire another person who can share jobs with me and have say 2-3 of us on the same 2-3 different projects in parallel to cover the lack of cover 20% of the time. We need to be really zoomed in on the problems to solve and tasks to do - not being there 20% of the time couldn't possibly work.
The dream of a 4 day week is for many, many workers just that - a dream.