I almost have at lest a extra quart that drains out after I sparge, drain and squeeze. Whatever's left under the grain bag when I get done with the boil goes into a jar and into the fridge. After a couple of brew days, I've got plenty to boil up for a starter. As for an extra sparge specifically for that purpose, I suppose I could get a little extra, but I don't leave much sugar in the grain by the time I slow-sparge and the last of my runnings are in the 1.025 range. If it was a big enough mash, it might yield something, but if I ran another sparge of a typical batch, I wouldn't be pulling enough sugar to make it worth the trouble.