I belive that 3. But it could depend on your hashrate, best - check it for self
20 hours ago i tested dwarfpool.In 3 hours of mining,I got tonns of rejects. I had to wait 20-60 sec for new jobs. Accepts 100...3000ms. (ping to zec-ru1.dwarfpool.com 50-70ms)
now after 1,5 hours -- 0 rejects. but 5 hours no block found
