The monthy thread is there for the community to post their desktop(s) sceenshot for "the month". I have three systems I use daily, my office desktop, laptop and home desktop, so I wouldn't feel bad posting all three in a day.
I don' t think it bothers anyone if you post a shot or 2 a week but if you wish to post one every day or multiple shots per day then the Screenshot library is a better solution. The trick here is not to have a few individuals who account for every other post in the thread.