I've heard of some people having great success flushing out the brifters such that the brifters now have more life on them post-service than they did before they started getting stuck. It can really bring one back from the dead. But you never know for sure how long it'll last.

I think that in your climate (I'm from coastal Georgia, so I know how different my bike parts behave when I take it back home), you might want to take extra care with the brifters in the future when you clean your bike. Maybe give them some extra lube or WD-40 and lube every few months and when you wash your bike (which you probably do more often than those without all that salt and sand), be sure to rinse out the brifters as well as you do the drivetrain. It might help your next set last longer, though it could be that your current one dying is just bad luck.