Tubes made today are not as good as they use to be; manufactures to save a penny a tube have cut out the rubber reinforcement grommet that use to be at the base of the valve and this is why we have a lot of failures today in that area.
To combat that potential failure area some mini pump manufactures have come out with pumps with a hose, if you keep slack in the hose while pumping the natural tendency to "saw" the valve back and forth while pumping, especially at higher pressures, is virtually eliminated by the slack taking up that movement and stress on the valve. So be very mindful when pumping on the road that the valve doesn't move.
Specialized is the only tube manufacture that I know of that still beefs up the base, they don't use a grommet but they did increase the base thickness substantial over other tubes I've seen that have nothing. So far in over 15 years of using them I haven't had one failure at either the base or the valve itself; and if I blow a tube up outside of the tire to find a leak I haven't yet got a spot in the tube that swells up a lot larger than the rest of tube because that one area thinner than the rest of the tube, so their wall consistency is the best I've seen, even better than the famed Continental.
I bought a thorn resistant tube from Sunlite for my wife's bike (she doesn't know how to fix a flat so I have to make sure she doesn't get a flat because I'm not always with her), anyway this piece of crap had no reinforcement whatsoever, and a poor method of securing the valve to the stem with nothing more than melted rubber which was very thin and sloppy applied, it leaked out the base before the tube got to 20 psi. I took it back to the store and went to another store and ended up with Bontrager thorn resistant tube, while the base of the stem and tube is much neater, it didn't have the grommet but it may not be as necessary since the tube is thicker.