i'm still figuring out when and how often i can wear DS. i have a stretchy wrap, a mei tai that i made and an ergo with the infant insert.
around the house, it's usually the stretchy wrap because i like how i can pre-tie it and pop him in and out. also, it actually holds his head in place while he is asleep so i feel like i can be truly hands free, and it has the lowest profile so there is not so much out in front of me. it can get rather hot though and my back will start to hurt a bit if i use it for too long.
the mei tai i have been using for grocery store trips with a car (though i'm not crazy about the ends dragging on the ground when i put it on) short outings, and putting him in around the house/yard when i don't want to take the time (read: can't put him down long enough) to tie the wrap. the mei tai is the coolest of my carriers, the quickest/simplest to put on and the most versatile. i really love it.
the ergo has been great for longer trips out of the house, around town and when i have to go on the bus, ect. it's very comfortable and the insert is actually pretty neat too. i can take him out of the carrier, leaving him in the insert and can put him down wrapped in it which he seems to like. the insert does make him hot though and i don't feel like i can use my ergo on hot, sunny days.
i wear him 2-5 times a day i would say, either around the house while i try to get things done, or to get him to sleep so i can possibly put him down for a bit. i also wear him whenever i go out of the house because we don't have a car so i am usually on the bus. right now he is in the ergo and has been for about an hour and a half. wearing him puts him right to sleep so i will either leave him on me for his whole nap (mostly when we are out and about) or pop him out and put him down to finish his nap while i putter around and quickly do things i can't do with him in front of me (like unload the washing machine).