Expressions are always great, anyway remeber that animating rotations could be a bit tricky...
If you use the manipulators for rotating an object and than you key that position, Maya will convert it in a 0-360 range. So if you try to key for example 3 rotations, Maya actually key only 1!
If you wish to key rotations for values greater than 360°, than you have to write the value in the rotation fields whithout using the manipulators and keying that field.

Hope this helps