I seldom reply to wall posts. I do it probably every couple of months and respond to all of them at once. I have 7 pages of wall posts to respond to.

Something tells me I may not reply to them for another several more months
I plan to, once I catch up on all of them, begin responding to any one wall post within a week of receiving it. Let's hope that actually happens because I make that commitment to myself every time I respond to them.