How long does buttercream last? I made buttercream monday & I need it on the 17th, will it still be good?

what recipe do u use?

1 cup vegtable shortening, 1 tsp vanilla, 1 lb of powdered sugar, 2 tsp water & salt

Yes.. it will be fine. Stick it in the fridge until the day before you need it and let it come to room temp before you whip it up for a bit.

that are in advance, if it were me, I would freeze it; however, you probably will be ok in the fridge.

I'm also curious "how long" it lasts. I use a half butter, half shortening recipe, and have frozen mine a few times, but I've also left it in the back of the fridge for a week if I know I have another cake coming up the next weekend (I use a 12 c recipe)
How do you know if it's "bad"?? I always taste it before icing anything, and it always seems pretty good. The only time I've thrown it away is one that i'd forgotten about and became seperated and oily.

Thanks!!

In reality you could leave it out on the counter for a week and it'd be more than fine.. it is shelf stable. The ratio of fat and sugar is so high that nothing will grow.. even if you have butter and milk in there rather than crisco and water. There is nothing in the posted recipe that would spoil. Crisco doesn't need to be refrigerated.. nor does powdered sugar, vanilla, water, or salt. Put them together and nothing changes.