Depends on the bag and climate I guess. At a minimum you should cover it so it doesn't get wet. If I were you I'd get an old bag for outside use, or make it easily removable.
I got my bag outside hanging off a bracket. I kept the plastic bag it came in and just cover it with that when Im not using it.
Yes i have. Spent ages worried about how to do it and weather the wall will take it but its been there 12 months i reckon now with no problems. Only a 75lb bag and i do keep the actual bag in the shed and lift it up and attach it when i need it pain in the arse but its canvas and i live in england so dont think itd take the weather
I was thinking i'd be alright if I took it off the wall when I was done with it plus that'd be like a workout finisher.
Just make sure you keep a video cam going everytime you're hitting the bag. So when you eventually miss and smash your fist into the wall, we'll all be able to have a good laugh watching it on youtube... :yep