No.

You can decrease the framerate, which you might do to conserve resources, but the framerate cannot exceed 30 frames per second on the phone.

The line I am referring to is:

TargetElapsedTime = TimeSpan.FromTicks(333333);

Although the emulator will speed up, the phone will not, yet another reason to have a phone to test with.

Seriously, to mess around with this is more advanced, and only do it when you are early in a project, not late in a project.

When I tested this it just messed with my brain, but it was kind of interesting.  No problem to generate a little code to test this, I used my bouncing ball example and just changed the number up and down and watched what happened.  This is in a previous blog entry:

http://bit.ly/BounceBall

Have fun.