Mine have 30,000 miles on them and have no signs of cracking. That's not easy, smooth, highway miles either. over 90% of that is stoplight-to-stoplight riding, going cross-town to work every day.

Now maybe there were some defective pipes sold, but I'm thinking that maybe people are being careless with the assembly.

For one thing, the V&H pipe always seem to come from the factory with big burrs on the header pipes, where they slip into the mufflers. Also the mufflers have welding burrs inside the inlet ends. These must be smoothed off with a grinder before you slide the mufflers on.

Also it pays to use some anti-sieze compound. What you do not want to do is take a 2x4 and start wacking that muffler onto the pipe. I think you'll cause damage to the head pipe, and at some point you'll want to change the rear tire or grease the driveshaft & that muffler's gotta come off! Do the hand fitting up front and save yourself some time and effort later.

Finally, don't tighten anything completely until everything's together and lined up just right and all the bolts and nuts are on and just barely snug. Then you can torque things down. As you do it, make sure nothing gets in a bind because the muffler isn't on quite far enough or the rubber mounts aren't quite lined up. Make sure your engine mounts are torqued down as well, so there's no excessive vibration transmitted to the pipes.