Nope... NPK is NPK; it might get hard and clumpy and harder to use; but I would guess it will still be the same. I don't know that fertilizer has an expiration date.

should be fine, about 8 years ago i bought a bunch of MG fert, it was on sale. i stock up on a lot of stuff when its on sale, like food, toiletries, ammo, etc.

Thanks. I've heard conflicting reports and never knew what to believe about keeping old fertilizer around. Great info!

I was wondering about the same thing too. John, thanks for posting the question.
The only concern I have is the slow released fertilizer... the coating might break down over time so it might not be slow release any more.

As long as the fertilizer isnt liquid or has beneficial microbes in it it will last pretty much for ever. If it has beneficials in it, they would die but your NPK should be fine.