I was driving along the freeway behind a semi-truck when suddenly a
small piece of debris flew toward me and cracked my front windshield. 
I want to get this fixed, but I heard that replacing the front
windshield won't be as durable.  Is that true?  Please explain.

>> I heard that replacing the front windshield won't be as durable. 

As durable as what? A replacement windshield will almost certainly be
more durable than a cracked one.

SOme places there are laws on how long a crack may be before it is
required to have the windshield replaced  - and cracks get longer
under the strains put on the glass.

I have also heard that in some modern cars, glued on windshields are
part of the calculation of the vehicle's stability (not that of road
performance), another reason to have a damaged one properly replaced.

What they mean is some aftermarket windshields are not as durable
As the OEM glass your car came with. That?s why manufactures recommend
always using OEM glass because the aftermarket glass tends to crack
and break easier.

Also, from experience I know that the seal around a replaced glass
will not be as strong as the orignal seal meaning you may eventually
get leaks around a replaced windshield.  However, being that your
current windshield is cracked, it has to be fixed for your safety.  If
it is very small and not in your direct line of view, there are ways
to fix the crack without replacing the glass.  If you have a large
crack, it will continue to grow and become increasingly unsafe until
you have it replaced.

I'm a ASE certified mechanic with 30+ years experience in auto repair.
 First, let me say there is nothing like replacing the glass.  It's no
big deal, many glass folks will come to you.  Your "comprehensive" 
part of your insurance should pay for it.  One of these companies pops
up as an ad above this question: safelite.com.  The glass does indeed
form part of the structure on a lot of cars.  A urethane adhesive is
used to secure it in place.  Any reputable glass shop can install this
properly, and providing he doesn't scrape a bunch of paint off under
your molding to start some rust, the strength of the car is
unaffected. more of this sort of thing on my website: econofix.com I
give advice for free. More advice: If it is a small "bulls-eye" and
not in your sightline, there is a resin repair system available.
gtglass.com makes one of these systems: I have never personally used
it.

Depending on the state/country you are in, you might be required by
law to get it fixed. If it's not cracked all the way through the
glass, then repairing shouldn't be a problem. If you have to get the
glass replaced, just make sure that it's not someone dodgy, because
there are plenty of horror stories about people getting taken for a
ride.

www.autoglassrecycler.com.au