I have the Indian generic Kamagra 100mg.
The expiration date stamped on the blister packs, is 07/15, and I bought them about 6 months ago. So I think we are looking at about a 3-1/2 year shelf life.
I live in a hot, tropical climate and have previously stored the product for over a year, unrefrigerated, with no noticeable decrease in potency (pun intended).
I've never bothered to refrigerate mine, but storing in the fridge should extend the shelf life, since most chemical reactions and/or biological activity slow down at lower temps.