I did a peek at Stalingrad-to-Berlin
Battalions = 11 T34, 20 T61, 5 KV1
Regiments = 23 T34, 16 T70
Brigades = 32 T34, 21 T60, plus other support elements
Regiments over battalions (no cost?)
Brigades over regiments if I can spare the points
I start scrapping the battalions once I have enough tank SUs to backup the Tank, Mechanized, and Rifle Corps.
I build out to the maximum number of brigades, then keep as many regiments as necessary to provide for a quarter of them back in STAVKA refitting.
Typically, over half of my tanks are in SUs.
My normal practice is to pull all SU less than 25% of maximum, and like to do it when they fall below 50%.
That way, I can keep the on-map ground units in the field longer. (A 50% Tank Corps, augmented by 100% tank, mech, and destroyer brigades, can still pack quite a punch.) And, as long as I can maintain a defensive line, I will pull on-map ground units when they drop below 40%. I put them in REFIT, at a nearby depot, usually with an HQ unit, and normally keep them there until they reach 90%. In an emergency, I can put them back in the line with the best SUs I have at STAVKA.
That means, though, I have a ton of units under 65%. I think Zhukov, like Montgomery, wanted everything at maximum strength before commencing operations. I'm more of a keeping-hitting-them-with-good-enough, and never giving them a chance to reset.
More than you wanted, I think, but I can't help myself once I get started.
Regards,
Rick