I have 10 Th/s for more than three months, all S1s , and never found any block.
You're God damn lucky!

I agree, he's lucky.
I've been mining 24x7 for 12 months and have never found a block. I've had a reasonable hash-rate too, currently at 5 TH/s.
If you are mining with a "traditional" pool (not a solo mining pool) then this should really not matter to you as you will get paid regardless of the amount of blocks that you find.