As in you become more sensitive to it or less? I've never heard of either before.
I take it probably 3-4 days/week. I take a 7500mg complex standardised to 40mg flavonglycosides. I has some synergist compunds in there too - ginseng, gotu kola, tyrosine etc.
I notice that I'm slightly more alert when studying and working. Don't think it does anything for my gym performance. Not nearly as cool as when I was on a proper nootropics stack, but alas, that is more than I can afford at the moment.