1 L is good for 20-24 rolls of 35mm, according to the specs, so 1/4 of that is 5-6 rolls. Find the equivalent surface area of 4x5 (saw it in a post here recently).
I developed 20 rolls with one midi kit this week, and the results were good all the way through, although the last 8 rolls were bleach-bypass. I kept it at 100 degrees F, and used Kodak's times and wash instructions rather than Rollei's. i also used Kodak's final rinse, since Rollei does not supply enough in the kit (what the hell is that all about?).