As a rule the yeast in a wine kit is good for longer than the juice/concentrate. Recent yeasts have had 2011 expiry dates. Some of the kits I would definitely not be making in 2011 (but others might).
When I ran my store, I had sales for 3 reasons...
1) older kit. ask the retailer about the age of the kitr.
2) sale from the supplier.
3) sale at a slow time of year to attract business.
For example, in an FoP, sales slow down as Christmas gets close because customers cannot get the wine bottled before Christmas. I might have an advertised sale that incorporated kits on sale from the supplier.
Steve