I've never used that technique, but a variation on it.
There is some large German word for this practice which escapes me at the moment, but when we brew 4 batches of Imperial Stout or Barleywine in a row we will save the last 7bbls or so of runnings from each batch and dough in the next mash with that wort. It helps get our gravities where we need them for those huge beers.
An alternative would be to take the first runnings of one mash and boil those while mashing in a second time and then combining them both in the kettle for a more efficient method of reaching a high gravity.
Just my 1/50th USD.
Fighting ignorance and apathy since 2004.