Varies as it depends on how long the vendor had it on the shelf prior to selling to you. If it's a vendor that has high turnover, I think it's a pretty good amount of time.
My Salifert Alkalinity kit from BulkReefSupply was bought about 3-4 months ago, and I just checked - exp. 02/2017.
Gotcha i bought 4 alk cal mag and ph all from the same place about 1 1/2 years ago and none had expiration stickers. wonder if i got taken on this :/ urggg now i need to get new kits to be sure.