I would like the discard old build feature to have an option to always retain the last N builds, regardless of their age. It looks like "Max # of builds to keep" will keep the last N builds, but this is NOT what is does: the "Max 1 of builds to keep" does exactly what it says: once the max number of builds us reached, the oldest builds are deleted, so as to not exceed the max. But the "Max # of builds to keep" is overwritten by the "Days to keep builds". So if you need to keep the last N builds regardless of their age, it is not possible.