It runs one game at once after 2 hours. Because playing more than one game at same instance reduces the drop rate.

Thanks for the answer and yeah you're right. After 2h of playtime (made by IdleMaster) it started to drop cards. Maybe I got any connection issue this night when I left pc turned on

Here is a print, left computer turned on all night, but didn't drop anything.

http://i.imgur.com/yE59R0a.png