I do that with my wallet and keys. I rarely take my phone out of the house though, and even leave it switched off for days or weeks at a time. I'm not sure what I'm missing out on by not having it available 24/7.

It's a very liberating feeling once you have 'trained' your friends and family that you are not dead nor hate them if a text goes unanswered for a few hours.

That is orthogonal to having a smart phone on you 24/7. I trained my friends and family not to expect instant replies (or me always picking up phone calls), but I use the phone also to read stuff, search for stuff, and note down stuff, so I do want it on me all the time.

I'm usually in the same place, and using my Linux desktop. I guess that's why I've always found it hard to get interested in phones: annoying devices with too-small screens, slow data entry and usually a locked-down OS with no updates.