Yesterday, I finished composing the last entry taken from an item in Suggestion Box 3. My prediction that the backlog would clear in early 2010 was off by exactly one year: The last Suggestion Box 3 entry is scheduled to be posted on January 3, 2011.
I figure I'll open Suggestion Box 4 sometimes next year. But I'll leave it open for only a little while, to avoid the problem with Suggestion Box 3 where I left it open for so long that it took six years to clear out.
(Then again, maybe I should stick to a six-year cycle for emptying the Suggestion Box. That would certainly discourage people from putting "Please help me with my problem" type entries into it. Unless they're willing to wait six years for a response...)