I think this is more a function of starter size. One vial in a small starter will not result in much growth, but 1 vial in 2L starter with stirplate will get you over 2X growth. Obviously growth is a function of time, but all of the growth should be accomplished in 24 hours.
Well, that's helpful! Thanks! So just do a 2L starter on a stir plate for 24 hours. I think in a five gallon batch I will want to let the yeast drop out and pour off some of that wort, right?
At a 1.092 OG (22 plato) you are asking the yeast to do a lot of work for you. If it were me, I would probably brew a smaller gravity (1.050 or under) beer first (with a sufficient starter of course) then use the yeast from the primary to kick start your big brew. Kind of like getting two beers for one (more or less).
If you do a 2L starter, you will want to chill it down for at least 24 hrs (depending on the yeast's ability to drop out), then decant the spent, oxidized wort, pitch your yeast and aerate.