All figures for D76 1:1 which I have seem to assume development in small tanks without the need for extra volume, so four at once in one litre would be the regular process for the times given.
As far as print developer goes, these days it is hard to find a paper that has no developer embedded - most PE base and VC papers will develop in a tray of alkaline "activator" that does not contain any developing agents, so the condition of paper developer usually needs to be little better than "wet". And even with classic paper, you can use the developer until the blacks aren't properly black any more or the image tone takes a odd turn - other than fixer, which can turn bad without warning, there is nothing hidden in the developer stage that escapes a visual test and requires chemical control or computing the used area.