Should I pitch two vials for high-gravity Imperial Stout?

I'm going to brew the MoreBeer Imperial Stout AG kit this weekend. I'm not sure yet what the expected OG is (I've not received it yet so I don't have the specific breakdown on the grains) but with nearly 18 pounds of grain I'm assuming it'll be pretty high.

I'll use one of the White Labs yeasts (not sure yet which one) and normally I'd make a 1 qt starter the day before. For a higher gravity brew like this would it be prudent to pitch two vials? I don't mind the extra expense if it'll be of actual benefit. I'm inclined to make the usual starter from one vial (to insure viability) and then just pitch a second vial directly. Helpful? Wasteful? At what gravity does double-pitching make sense?

Yeah, I know I could start with one vial and step it up over increasingly large starters, but I'd rather not monkey with that.

Just make the bigger starter. It's one more step-up

niquejim said:

Just make the bigger starter. It's one more step-up

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+1 a 2L starter @ 1.040 should be plenty of yeast.

Using two vials to make a starter gains you nothing, unless you want to use two strains of yeast. By the time a starter has finished growing, you should have 10-20 times as many yeast cells as a vial.

If you are really worried, make a lower gravity ale first and pitch the Imperial on the cake. That's like having a 5 gallon starter!

I made a 2L starter for my 1.090 Tripel last Wed... on Thursday night I put it in the fridge, on Friday I decanted half the liquid and added a quart of 1.080 wort (back to 2L). On Saturday I pitched the whole thing in. Fermentation was... uh, violent at 66.