Replenishment is really only useful if you're developing quite a bit more than that. For Xtol though, one would normally replenish one roll's worth from a 2L working solution after about 1-2 weeks of inactivity. But your process isn't going to be very well controlled with those big gaps being the norm rather than the exception.

If large-volume tanks are causing you wastage (i.e. quantity required for coverage is much greater than quantity required for capacity) then you might want to look at using more-highly-diluted developers. Too bad if you wanted silver-solvent (grain-smoothing) effects though.