Depends on the developer and the associated breakdown and oxidation products.
With ID-11 and D-76 you can chemically buffer the developer so that the "as-mixed" activity is the same as the "aged" activity. You can also buffer DK-50 and HC-110 (Pat Gainer will likely be heard from on these subjects).
For the most part, I use 1 shot developers mixed from stock concentrates for maximum repeatability and predictability. Notable Exceptions are Ansco 130, Agfa 8 and Diafine.