Avoid enemies with axes and your shield should be fine. My shield hardly brakes with 6 shield skill. Once you engage an axe wielding maniac its gone though. Pick your enemies.
This x1000.
For OP:
Also make sure that you're fighting back, or at least threatening your opponent. If your opponent doesn't think you're going to attack, then they will just spam your shield as fast as possible until it breaks.
Even if you just get into the "i hit you, you hit me" rhythm of trading blows on shields, your 7 shield Huscarl's should outlast that of most opponents. Also, trading blows has the effect of reducing their overall attack speed (since they have to spend half the time covering up from YOUR blows) so your shield will stay alive significantly longer.
Disrupt the rhythm with feints/held attacks (attack when they think it's their "turn" to), and you've got the most basic strategy. (Just watch out for them doing the same to you!)