I can only confirm that!
Since I am in the signature campaign at Freebitco.in (now also already in the 19 week and I hope the campaign continues for a long time) I have also generated some refs through my signature...

However, where all the clicks on my link come from (in only 30days), remains a mystery to me!

I think this will be a long term signature that's why even there's some more higher pay rates campaign I tend to stick with freebitco.in. I think that's still fine you may not know that 1 user may deposit huge balance or may win a huge jackpot you'd be earning too. That's too many clicks but only one signs up and seeing your profile posting on different boards that isn't unexpected on your end more likely on your local board or here in Gambling board.
Referral income here is definitely one of the best plus it also depends on the type of people you gather as well. I have been doing it for over 2 years now, not a huge investment or not even a time, I found a small bitcoin related website and they were asking for just 5 bucks for advertisement, talked to them about being there permanently and agreed on a deal, now my freebitco.in ref link and banners are up there for the past 2 years or so and people constantly come from there, not a huge number, there is like 3-4 clicks everyday, most of them do not even stay.
However what you realize soon is that some people are there just for faucet, and they leave very soon after because you can't just use faucet here and be done with it, you need to see the other great parts of it as well. However some of them decide to use it fully and those people stay for very long and make you a lot of money.