Can't guess your earning but 2000 impressions and 40 clicks, that is really good. I don't get that too many clicks with the same amount of impressions.
If you are already making a daily income from adsense I would definitely not change the niche you are in. That would be stupid, I would try to exploit the profit pig you have in front of you.
I say keep working on it. Who knows maybe later your earning might increase. It's definitely better then getting nothing at all.
Is that you earned from your clicks . Can you share you niche with us . If it is from image hosting site than it must also cross $4 atleast lol .
ya i cant change the niche.. am ok with wht am get now. but i think b4 with much more less impression and clicks i got the same earnings only .. no increase in my earnings for more than 6 months ... i wish for wht others said above ...