Pam,
Have you considered trying downtube shifters? I have always loved bar end shifters, but one of my bikes has 9 speed downtube indexed (gasp!) shifters which are just wonderful to use, and are my current favorites. They are Shimano Dura Ace, but these seem unobtanium nowadays. Microshift and Suntour both have options though. Shifting both derailleurs simultaneously can be performed with one hand and the short cable run and absence of shifter housing (except at the rear derailleur) mean there is almost nothing to gum up with bad weather.
I have never had a cable head seize in a downtube shifter, but that could be coincidence. I really like the grease/anti-seize idea Mike Godwin mentioned.
IanA Lake Louise, AB Canada