I have a coorie pouch sling and I have used it constantly since DS was teeny tiny and he's now a strapping 22lbs at 7 months and I still use it all the time.
I pop him in it whenever he wants to cuddle up but I don't have time to just sit with him, I put him in it when I am just nipping into a shop for a couple of things, I put him in it when we go visiting people, I put him in it to go the post box, I put him in it when doing a hospital visit, I put him in it all the time. I wouldn't set out on a long walk, or an all day shopping trip, but whenever I want him close, or getting the buggy out would be a hassle, and DS is too heavy to carry further than the end of the garden, then my Coorie is perfect.
It take a mere moment to put on, totally foolproof, not a strap or adjustment in sight, very comfortable indeed (I've got a dodgy back too).
When he was small I could actually bf him in it, meaning I could walk about the house or sit to table for my tea and feed him at the same time.
He has always fallen asleep in it and still does, and when he does, I can lay him down and slip it off over my head without waking him and it just acts as a fleece blanket for him.
It also doubles as a cushioning pad under my travel changing mat, as a pram or buggy blanket, as a nursing cover, and once even as a makeshift nappy. Washes up lovely and virtually dry coming out the machine.
Best baby thing I ever bought.