Originally Posted by
banerjek
Easiest way to deal with this is never have old cables/housings. If you replace them regularly, chances of heads pulling off, cables seizing, or even decreased performance drops dramatically while you get a lot more miles without needing to fiddle with anything.
Another +1 to you. It seems we are of the same mind here.
Op, ideally, do the work once.
It is already too late for the housings, the damage is done. Spraying with WD-40 is a temporary fix that will still leave you with spotty shifting and then back to cruddy shifting again. Not a solution unless budget is an issue then this will indeed buy you some time to shop for a deal but shop you will.
Another consideration is where you are riding. If you are riding in a winter climate and there is a lot of moisture or road grime, I might just tough it out for the winter and live with the shifting (and a handy can of WD-40 and a compressor) and then install shiny new cables, housing and tape for spring.
Any way you go you will be replacing the housings soon, at the very least.