I don't get the fixation on extreme high quality centers.
There are many places in the game where number of soldiers is important, or more important than quality. Takeovers, looting, civil work and many others. Cheap units that you can mass-recruit have always had a place, and the best advise in my book was the one telling you to look for what the realm already has and try to cover out what it doesn't.
And never forget that the next try could get you something worse. So if you get a long-range archer unit with very low armour, you just might want to suck it up and keep it, because who knows how long you have to try to get one with the same range an better armour.
