How long does royal icing last? I made some for a cake I made a couple of weeks ago. The leftover icing has been in the fridge. Is it still good, or do I need to make more? I made it using pasterized egg whites, powdered sugar, and a little lemon juice. Not a big deal to make, I just hate to throw this other out if I can still us it. Thanks for you help!

Rebeat it and see if it fluffs back up to it's original consistency. If so - it's fine. If not (and if it's not growing green stuff) you can just mix it in with your buttercream - if you use a crusting buttercream recipe, that is.