Some of you may know that I made the mistake of buying a off brand ebay downpipe which resulted in an incorrect fit that I had to fix with a drill and some elbow grease and an annoying vibration of the DP rubbing the bottom of the car. I decided to buy some header wrap at a local automotive store and wrap the hell out of the spot that rubs. I ended up wrapping the entire thing and got more than I bargained for. A. The vibration IS GONE! B. Reduced high frequency exhaust noises. I got the exhaust sound I've been searching for. I recommend it to everyone.
So far I've put about 300 miles on it and been through some driving conditions that I cannot speak of on this forum. The DP had remarkably good welds on it and 3/8 in flange. They claimed it was stainless steel but more than likely it was nickel plated iron. So far so good. If it does crack I'll just have to buy a name brand one.
You shouldnt have to worry about the cracks as much as you should corrision which will then lead to crakcs. But if you rappwed it and the DP was in good condition, clean it should last you a good while before, if any, misfortune happens upon you.