I wear as needed. When Josh was younger I would wear him more because he wanted me two. And I could tend to him and get stuff done. Oldest Alex was not worn as much because I did not have any other children at that time and the need to wear him as much was not there.
I don't wear DS much anymore, but he is 18 mo and big!
When he was little, the sling was a life saver when he was fussy.