I've done this a few times. Yeah it's a bit of a hassle, but I enjoy the process and I don't make big beers all that often.
Make a 10L batch of high gravity liquor, boil and add hops and all that.
Cool it and add it to the fermenter - add the yeast. 10L of 1.070 (or whatever) with the yeast breeding up nicely just about to start fermenting.
Make another 10L batch the next day - exactly the same recipe.
Pour it on top of your last 10L.
20L of 1.070 beer with a ripping healthy yeast already having a headstart. It's like you made a 10L starter.
yeah actually, that sounds much better.
that, and i dont have two bags.
haha cheers for that quick refresher, i think im back up to speed. boiling the water as i type! wish me luck