I think it makes sense to have a fresh new poll quest for every year. The reasons are:

• keeps each year's thread a reasonable length
• it's ok to repeat some polls after a few years, since opinions (and monks) change over the years, and it's interesting to see that too for some poll questions
• it's really not that much trouble for a prospective poller to click two or three links to review past year's poll questions before posting their poll suggestion
• using the "2007" poll idea quest thread makes no sense since it's 2008. It also makes Perlmonks look out of date to newcomers (either when they go to submit a new poll suggestion, or when they see a new post on it pop up in Recent Threads).
• It's not sustainable to keep just one poll ideas quest thread going and going.