Many people post on multiple message boards, so it is quite common for such posters to not check everyday for replies.

I will commonly leave a thread/debate alone for days at a time until I have the time or desire to respond. It sometimes takes a while just to compose what I consider to be a proper rebuttal. Other times I am waiting for others to post their opinions as well.

Locking a thread is not usually needed, as it will eventually drop to the bottom/oblivion as new topics are created.