I use Sunlite on my bikes. My Phat Stretch has the same tube in the rear tire that it had when I bought it back in March or April 2012. My front tube was replaced 6 months ago thanks to a nail in the road.
Tire company and lbs branded tubes are usually better than X-mart (Oh Schwinn, how the mighty have fallen ) but there's often some issue other than tube quality involved, such as loose valve cores, shifting rim strip, or the tube sneaking in between the rim and bead. Also, if the valve is one of those long ones with the spring and spoon on the end, it can cut into the tube during handling or installation. :roll: Good luck my friend.
I thought the same, a long spoke, bad rim strip, tube slipping etc. Everything looked good no signs of any issues, that could damage the tube. But now I'm up to 3 tubes, all splitting in the same location, on 2 different rims, I believe this batch of defective tubes.
I bought a couple of the Hutchenson tubes, since their made for up to a 2.35 tire. I hope all is good now, if not I'll try the Sunlite tubes.
Thanks for the help. Kenny