well, the packets have just been sitting in my purse since i bought them (i was using them before, i just had them all in a baggie). now that i think about it, they were more like 2 years old. our place tends to get quite warm, so maybe it did break down a bit. i've used sweet & low (i think that's what starbucks carries) & the granular form of splenda, & i was fine with them. the coffee was so bitter it was undrinkable i'll toss the rest of them.