I decided to keep my triple, so I am upgrading from 105 levers (20K miles, LOTS of shifting, at least 6 RD cables snapped). I bought a new 6703 lever set from Ribble ($253), have assembled them at my desk, and have questions (as always).

1. Does the RD cable last longer than those in the older design?
   • My 105's are 2008, so probably 5500?
   • After my frequent breakages, I carry a spare cable, but I am an idiot that I haven't been replacing the cable every six months.
   • I think it's breaking more often now. I use Shimano OEM cables. I have not changed the type of riding or length or rides or my weight, so I think I do the same amount of shifting. The FD cable has never broken, of course, since it doesn't get used very often. When I have replaced the RD cable proactively, I replace both.
   • I.e., should I plan on replacement every six months?
2. I will tape my bars such that I can access the cable housing - replacing a broken cable on a ride is enough of a pain w/o needing to re-wrap - any problem with this idea?
   
   
3. Is shifter mechanism corrosion a problem?
   • The boot seems to expose much more of the mechanism than my old shifters. I live in NE, I tend to push the season, although I hope to create a winter bike out of my 1975 Lotus.

Feel free to offer suggestions, warnings, or opinions. I am asking in this forum because I value your opinions.

Thanks.

No. Shifters with an internal 90 degree bend eat rear derailleur cables.

I used to get 4000-4500 miles with older Campagnolo levers with the bend in the cable. New Ultrashift levers including a 90 degree guide fray rear cables in 2000-2500 road miles.

The issue is fatigue. Additional bending (not just around the shift drum) means more of it with shorter life.

Base it on miles, or notice when shifting degrades - shifts to smaller cogs get a little sluggish before the cable breaks all the way. If you need to reduce tension in the cable look at it ASAP because you've gunked a housing, frayed a cable, or bent the derailleur/hanger so it's closer to the spokes and may break things when it goes into them.

Carrying a spare cable/ doing a repair like that on the road seems crazy to me. I can't imagine having the patience/ tools to do it well enough, and a substandard repair is just setting yourself up for repeat failures. If a cable ever breaks on you, you can pick a gear and clamp it under a bottle cage bolt. You'll still have the front shifting (or rear if the front goes) which is enough range to get home. Carrying a spare cable is basically invoking the wrath of the cycling gods.

shimano 'upgraded' their shift cables and housing to help remediate the problem of the internal bend in the 7900/6700/5700 shifters. The new fancy set is SP-41
I have not tried them myself but heard good things

I actually did do this when it last happened, about one month ago. I was over 30 hilly miles from home, so whatever 3 gears (triple) I chose would have been difficult. As it happened, I did the repair on my favorite road,* the homeowner offered help (not needed), and it took less than 15 minutes, including dialing it in. I have not made any adjustments to it since then.

And, FWIW, it didn't seem like much of a hassle (I carry disposable gloves) and I was proud that I could do it.

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And, per other comments, I did notice the "feel" of the shifting change, but only a few miles before it snapped.

* I've always felt as though I've led a charmed life.

Yup, it's got that cable set. The cable and its sheath are much thinner.
(Edit: I thought it was, but maybe not. I'm too lazy to go outside to check)

The bad part is that my dozen (?) spare cables just became useless!

Maybe if you took less stuff you'd be able to ride over some hills without a babby gear

Since you are not intimidated by the repair, continue to carry your spare cable. You may be able to get enough slack in the cable to check it periodically. Shift to the largest cog. Then, w/o turning the crank, shift as if you were going to the smallest cog. The derailleur should stay under the large cog and you should have enough slack in the cable to pop the last piece of housing out of the chainstay stop. Push the slack inner wire toward the shifter a few inches and you should be able to see the vulnerable section. I may have this backasswards but try it.