I know the feeling. Once I was past the 200/240 mark, it seemed to slow down a tad until about 220...then I got the "blood in the water" mentality and started doing everything short of ARF spam to finish it off. RNGesus threw me a bone, too; 228/240, with enough umbrite/crystal dust for 3 turn ins on hand...3, 4, then 5.
Oddly enough, for the longest time, I had more of an issue acquiring the dust part, not the Umbrite. I could've remedied that with the leve/vilekin strat, though. I have 30 moonstones on hand currently plus full 100 leves available for the DRK weapon, so if I went ham on those, then I'd be all sorts of starved for umbrite.