In fact, 4 10s aren't much harder than 4 8s - for me travel time was dominant as I had to physically go run a lab. So I actually kept my salary while getting permanent three-day weekends. And I justified it by being able to get setup and cleaned up outside of normal work hours which was true and glorious.
This is true but in many companies they won't give you the 4 10s option. The reason is that the company can cut 20% pay but realistically set the same targets (where possible). So the expectations don't realistically drop by 20%, just the time you have to reach them and the pay. Depending on how much you were payed to begin with you may find this a reasonable compromise.
I did 4x9 also for a while, also with a long (1h15) commute. Was OK for a year, but I was glad that my next job was 4x8 again, with 1 day WFH. So 3 days in the office, 1 day from home. Perfect!
