Saren wanted to say that he was growing bored of this game. However, reality was much simpler and more embarrassing:

He genuinely hoped this chase would never end.

It was annoying at times, of course. The one hunting him was persistent beyond belief and he had half a mind to kill them and be done with it. He was a Spectre -- he had better things to do.

But none of those things were quite so fun and, honestly, when was the last time Saren had allowed himself to have fun?

It couldn't go on forever of course, all games of cat and mouse eventually came to an end. But he could very much enjoy it while it lasted.