If a particular developer can be reused, the specifications for the exhaustion rate and replenishment (if applicable) will be published by the manufacturer. This information is usually available on the manufacturers web site. The most common developer that can be reused is D76 from Kodak (or the Ilford ID-11 equivalent) when mixed to the standard stock solution. D76 and ID-11 are also frequently used in dilutions such as 1:1 or 1:3, in which case they are classified as one-shot developers. There are others such as HC-110 and TMAX developer, which have similar capabilities.(posted 8369 days ago)As the others have stated above, it is more difficult to get consistent results with developers that are reused. Many one-shot developers such as Rodinal used at dilutions of 1:75 or so are very economical, consistent, and the liquid concentrate keeps for a very long time.