Whatever one does for fun or for work, one is better off knowing the the ins and outs of the job, sport, task, object. If you tires are leaking constantly, you can bet that its YOUR falt, for not knowing what you are doing.
Like the one guy said, if your stem ripps away from the tube look at its seat, maybe it has a sharp edge, figure out how to smooth it. If your new tubes keep leaking, find what is puncturing them, probably something still in the tire. The nut on the presta valves sould be hand tite, not dicarded as is true for the caps. If you valve is bent, replace it. If your LBS can't fix it the first time, find a new BS. The only probs I've had with flats have been Goat-heads or snake bites, and once a valve that got junk in it (shrader), so I cleaned it out. If you realy like biking but your bike came from from a dime store, maybe look to a better bike. there are a few good bike review sites on the net, do your homework, read up on the right equiptment. OR, keep being a victim, your choise.
In other word people, take responsability for your actions and things and you'll no longer have such problems.

You know this thread is over a year old, right?