It's not worth it late in flower.
At 30 days of a 2 month flower cycle you aren't going to make enough difference to justify the possibility of having residues on your buds. Ick.
Plus the extra moisture could lead to mold.
Generally no spraying after week 3 gives you safety for 2 reasons; 1) bud formation is still really minimal so you won't get mold 2) you aren't exposing buds to potential contaminants that you could end up smoking.