The closest I have seen reinforcements come to running out in a long time was last night. The Russians got down to 4%. We still held the entire Admin building though...
Personally, I like it when reinforcements get close to running out, makes most players play smarter and the battle seem more intense. Hopefully, the running out part doesn't happen till the last minutes of the game. Must be hard to come up with a balance to where that happens when players are being smart, and also to compensate for a few bad players than can really tank your own reinforcement levels.
(Such as on Berezina...) it is one thing to loose near the end of a round after a good fight by running out of reinforcements, and another to do so because there are some clueless players who get themselves killed needlessly by not playing smart and draining the reinforcements.
One thing the Germans have to do sometimes is to destroy the empty halftracks that sit around the battlefield. This way, the halftracks will respawn faster so the Germans don't have to walk the entire way....