I'd suggest two strategies that might make sense.
1) When HR responds to a specific coverage, they should also specify the timeframe it applies to so that down the road people aren't confused. As is the case in your example, you'd probably want it to look more like this.
- Associate asks the HR Space or Group about vision coverage.
- HR replies that it is covered 100% for FY 2012 and also adds a link to the doc where all the coverages are noted for that year.
- Plan changes with the new year
- Associate searches vision coverage and sees previous question about 100% coverage from FY2012 with the link to 2012 coverages
- Associate searches again for vision FY2013 and finds a discussion related to vision 2013 OR finds a doc with the actual coverages for FY2013 OR best case they just chime in on the 2012 discussion asking for the 2013 coverage where HR can answer it again like they did for 2012.
2) If you are looking to offer a more structured FAQ type experience, I'd recommend tagging/categorizing your discussions or using a doc as a Table of contents that links to the seeded discussions. At the end of the year, it'll be easy to pull the list of discussions by tag/category or doc and edit/delete/re-use them for the next year. The nice part about this is that you can offer a structured view of these discussions on the overview page using the watch a tag or the view document widgets.