They'll last a long time, I asked a doctor if there was any risk in taking expired medication and he told me that no medicines expire as such, they just degrade over time and only one or two he could think of degrade at a rate worth worrying about. To be fair, I didn't ask what the one or two were, but I'm sure you'll be fine with sealed, well stored rc medications, at worst you might have to heat and shake if they precipitate out of solution.