You get used to it...
Also, during the nights it was loosened a bit, yet still fully secure and inescapable.
Nevertheless, the first night is the worst.

Yikes! So what was your total time in the straightjacket?

Your experience brings to mind a guy that used to post on MF years ago. User name -h- , he played often with Amanda Wildfyre in Minneapolis. I think his record was something like 60 hours in restraints.....bondage bag I think(catheterized and hand fed). I recall he had a sort of cycling bite tube hanging over his face for water.

You can never tell but he sounded like the real thing and his story matched some things that Mistress Wildfyre posted on her blog at the time.

Uninterrupted I have spent 96 hours (4 days) in a straitjacket, with breaks up to 1 week.
However I am not looking for a tight bondage, rather to something that I can handle for long time. That renders me completely helpless, exposes me and in conjunction with the play breaks me slowly...
And we always prepare very well, including custom-made perfectly fitting straitjackets, and obviously play-partners that know me very well and whom I can trust.

Sounds very intense. I’ve always wanted to be truly broken down. That would be one way to do it.

It's actually not that intense, but it is very effective in wearing you down.