The freedom to schedule things during the day is very powerful and a huge factor in my wellbeing. Being able to for example spontaneously drop work for a few hours to enjoy the first beautiful weather of the year is worth more a lot to me psychologically.

Being able to schedule out of work things during "work" hours is amazing too! I've been able to have a level of involvement in volunteer and community projects that is not really possible on a nights & weekends basis. Maintain relationships with my friends and family who don't work 9-5s, watch their kids regularly. Go to those odd-hours sparsely attended religious services and grow different connections in that community too.

To me this is all much more sustainable than having a relationship to work where I grind away at it waiting for it to be over so I can live my life. There are risks here too, specifically boundaries as you mentioned. But when managed well it feels like work is just one of my obligations among several, rather than the time I suffer through so I can do worthwhile things instead.