It mustn't also be 20 minutes at a stretch, a user can log in, get to threads that interest him or her, air their views and log out, one can do this all through out the day, making close to 3 posts without actively being online for 20-30 minutes.

I am a student, and there are times, such as this in the semester when it's difficult to stay online for so long, but I enjoy reading threads on this forum and expressing my own opinions, I still come in at intervals and go straight to threads i like, such as this one, and write out my ideas. Though I'll be making less posts than i would/do when the semester ends.