Loosen the front wheel bolts.  Jack up the front of the car and put it on stands.  Remove the front wheels.  Turn the steering wheel to full right lock.  Looking from behind the axel, examine the driver's side CV boot while slowly turning the brake rotor.  Look at the apex of the valleys between the folds.  If you see any cracks whatsoever, think about changing the boot.  What you're looking for.  Also look at the circumference where the boot covers the edge of the hub, as cracks can appear there too.  What you're looking for.  Small, shallow cracks are a warning sign.  Cracks that you can put a thumbnail into are alarm bells.  

Repeat for the inner boot.  Since it flexes a lot less, it probably will be okay.

Turn the steering wheel to full left lock and examine the passenger side boots in the same manner.

The right (passenger) outer boot will tend to fail first because it's on the shortest axel shaft, which means it experiences the highest displacement angles.

If you want to see how far you can go on a boot with small cracks, that's your business, and it's your money.  The boot, clips and grease cost about $25 and it takes an hour or two to replace the boot.  The joint costs a whole lot more and it's a lot more work.  If you let the boot split, it's all over - grease gets out, dirt gets in and the joint will probably fail sooner or later.  You should be able to catch any impending boot failures before they occur if you will do this simple inspection once a year or so.  Again, I strongly advise you not to let the boot split, as it just costs more in time and money.

My passenger side boot developed serious cracks between the folds, but none at the hub shoulder (at about 70 Kmiles).  My driver's side boot had small cracks between the folds, but deep cracks at the hub shoulder (at about 85 Kmiles).  

You can also check the suspension bushings and steering rack boots while you're at it.

 to MAINTENANCE checklist