In XNA, the easiest way to do this is to just have MathHelper do the angle wrap-around for you all by itself, using code like this:
rotation = MathHelper.WrapAngle( rotation );
Here's what's going on, and how it works under the hood:
Your rotation value is expressed in radians. (Radians are like degrees, but instead of being in a range of [0 .. 360], they exist in a range of [0 .. 2*PI] or [-PI .. PI], where PI is an irrational numerical constant approximately equal to 3.1415927.
To answer your question: Yes, it's usually considered good practice to keep angle values within your selected bounds. As you'd expect, an angle of 0 is identical to an angle of 2 * PI which is equal to an angle of 200,000 * Pi; they all represent exactly the same angle. But because of how floating point numbers are represented in a computer, very large numbers become less precise, so it's usually considered a good practice to keep them close to zero when it's practical to do so.
In XNA, PI is provided to you in
MathHelper.Pi, and 2.0 * PI is provided in
MathHelper.TwoPi. So a straight-forward way to unwind your angle into the [-PI .. PI] range would be:
while ( rotation < -MathHelper.Pi )
rotation += MathHelper.TwoPi;
while ( rotation > MathHelper.Pi )
rotation -= MathHelper.TwoPi;
If you prefer the [0 .. 2.0 * PI] range, then you could adjust the parameters in the 'while' loops above, to use those ranges instead.
In practice, of course, you actually want to use the MathHelper.WrapAngle function that I showed at the start of this answer. But this is the basic idea of what that function does internally.