This is quite helpful as I'm due DC3 and was wondering how quickly I needed to wash the old ones and if I needed some new ones.
My first wasn't sick much but she suffered really bad nappy rash so we did lots of nappy free time so they were great for catching the wee.
Also something that noone tells you, but you should dry babys bum after wiping/cotton wooling and before putting on cream/nappy. Muslins are great for that.
As others have said, over your shoulder or under their chin for catching puke/dribble. Particularly if a friend or family member is holding them.
My second was a puker, so under their head in crib to make clean up easier. General clean up of puke etc.
You said you'll be FF so possibly less relevant after your milk stops, but I used to stuff my top with one at night as more comfortable/sustainable than disposable breast pads and meant I didn't need to wear a bra.
The big ones are great for lying baby on in a park or a not too clean floor. Or changing nappies in someone elses house. Etc.
I only bought a pack as was reluctant to fall for the MUST haves. But now I have gazillions.