I once got approached by a couple who were looking for a 24/7 baby girl as a little sister (the guy was to be the daddy, the woman already was his Little). Of course, when they first got in contact they didn't say it was supposed to be 24/7, they just said they were looking for a playmate, and it didn't go anywhere (thankfully) because I got a pretty creepy vibe from them and they didn't believe that I am a girl after skyping with them (apparently girls can't have short hair? I am biologically female, for the record). Anyway, I later found an ad from them where they described what they were looking for, and let me tell you, I dodged a bullet there.
Firstly, the new baby had to be biologically female. Okay, a bit exclusive, but still fairly normal. Then, she should move in with them. Weeell...I guess if you're aiming for 24/7, that's reasonable? Here's where it goes off the rails though: She would have to sever all contact with family and friends, she would only wear pink, never wear shoes anymore, always use diapers for everything, no phone, no computer, only baby food, no makeup, no books that aren't baby books...and they "promised" that her mind would completely regress to that of a baby. Not only that, but they specifically said that they "would like someone with a mental disability". What the heck? Like, no offence to sissybabypansy, I am glad this worked out for you, but to deliberately seek out someone vulnerable and try to brainwash them into behaving like a baby seems incredibly predatory to me.
So, yeah. That's my two cents on the topic of going 24/7. It may work in extremely rare cases, but as an adult with a regular IQ, with friends, family and hobbies, it just doesn't seem feasible.