What I do to avoid etiolation (which I have had problems with before) is to firstly stop watering my cacti when the weather gets chilly and the days get short. This is usually around October. I did just water my Pedros and I will probably water them only once more for the year.

Once it gets decently cold and frost threatens to hurt my plants I will put them in the garage where they get no light and will be cold enough to go dormant but warm enough to be comfortable. If it gets freezing or below then I'll bring my plants inside and put them downstairs in a cool room (no windows, no light). This usually happens after they've already stopped growing.

From my understanding it is better to keep them in total darkness for dormancy instead of giving them small amounts of light (which could cause etiolation).

No water and no light

Just shows what tough blighters cacti are, Nathaniel, that they can stand such callous abuse. This is treating them totally unnaturally, in the Mexican desert they enjoy light all year round, it ripens the growth from the previous season, and brings latent flower buds into readiness for the next season. Good light all year round is highly recommended by all cognoscenti of cactus cultivation.