As you can tell by my username I love to wear diapers and both wet and messy diapers too.
I once wore a wet and messy poop filled diaper for 48 hours which is 2 days straight and after the second night I got a rash with red bumps on my butt so I would never do that again.
At most I wear a poop filled messy diaper for 12 hours or overnight and then clean up, take a shower and change into a fresh diaper.
I gave up using the toilet now and only use diapers for both poop and pee and I'm happy.
I would not recommend trying to wear a messy poop filled diaper longer than 12 hours unless you like getting rashes.
Messy diapers feel so good but the rash doesn't.