No way a couple inches more or less makes a noticeable difference. If anything it'd be cable thickness/shielding/etc.
While XLR and other locking connectors are clearly more secure, I don't think there's anything wrong with using the standard jack they used nor should it be an early point of failure unless you're being rough with it or the contacts were just soft from the start (in which case I'd consider it defective).
If the jacks were so weak they'd be failing left and right on portable players themselves where you tend to plug and unplug more often... There's other headphones that use the same jack and I haven't seen widespread failures with them either, like my M-80. It's particularly nice to have on portables.
Its a good point regarding many portable players with 3.5mm jacks however it really depends how much strain you put on the cable attached to the Jack plug. You usually have fairly lightweight cable for ear buds on portables, where as if you try different (normally thicker) cables for on heads such as the X1's the amount of force is much greater on the same size jack and the socket connected to it.
In about a month's time I will relate my experiences with this issue. I will say no more at this point!!!!