Does a Devil ever get more Evil Pieces? The High School DxD anime explains the devil ranking system pretty superficially. On the one hand, we know that to revive humans as devils and control them, one needs evil pieces. The precise number and type depends on the individual, but that isn't really important for this question. On the other hand, we know that devils don't keep the same rank forever. Low ranking devils also sometimes get promoted to higher ranks, and eventually they could control their own servants and presumably stop working for that master at that point. Of course, low-ranking devils can also die.

In these situations, it would seem like a pretty substantial blow to the original master if they can't control any more devils. Their army's strength would be permanently reduced. Does that master receive new evil pieces to compensate in these cases?
I believe that even if you become a High or Ultimate Class Devil (Only two reincarnated devils have done so in canon) and obtain your own Peerage you still are a servant of your King. Kuroka was stronger than her King by a large margin but still served him. This means that instead of losing your legion you gain more legions (not proper terminology since a legion is over 5500 troops) that are indirectly under your command. Sirzechs peerage seem to be all high class but still serve him. Tannin himself is Mephisto's Queen but he is also a Ultimate-Class Devil and King and in the Top 10 of the Rating Game: in other words a hero of the Underworld. It is suggested that technically Tannin is still his servant but hard to confirm since even from the beginning Mephisto gave Tannin free reign to do as he pleased.

This is also supported by the fact that in volume one of the novels (and manga) Rias states that powerful peerage become status for their King. This would suggest such things remain even for servants that rose in status otherwise it would make more sense to make blood-status the requirement to get a set of Evil Pieces not Class since they would lose their property and the Devil's in DxD seem too greedy to sacrifice their valuables especially when their worth has become high.

Once you use it, Devils won’t be given a new [Evil Pieces].”
Quoted from Rias in Part 2 of the New Life Chapter in the first volume of the DxD novels.

Also I got this from the official DxD wiki (which holds copies of the translated novels):
There is actually no conflict when a Low-Class Devil starts his own group while still being a part of another peerage after becoming High-Class. When a Devil reaches High-Class, they receive a set of Evil Pieces to start their own group. However, even after going independent, Devils are still obliged to fight as underlings whenever their master has a Rating Game, for example, if Issei were to reach High-Class and start his own peerage, he would still have to fight as Rias' Pawn if she ever has a Rating Game. 

And Evil Pieces that have returned have already stopped functioning and cannot be used ever again. 
Said by Kiba in Vol. 12 of the Novels.