Hey, gotvim.
What you're experiencing is also being experienced by others. Either by lack of users or lack of organization in this forum, there are not many other instances of this issue.
You can read a little more through this thread and the links contained within; basically it's a resource leak, and takes some time to manifest itself in different ways. Basically your machine runs low on resources just like Windows machines tend to do.
Don't worry though, Apple will come out with a fix - hopefully soon.
Flash Player/Mac slowdown
Good luck.