CactiGuide.com

Several years ago I had to sever the head off a etiolated Lophorphora seedling. It sat doing absolutely nothing for almost 3 years, I checked on it today...
Amazing that it can sit seemingly dead for so long and then jump into life.

Yes, compared to "normal" plants it's amazing how long cacti can stand just dehydrating before rooting or growing. Unfortunately we are often too impatient for them to do so, but they work to a different time scale to other plants, both in growth and often rooting. That is how they survive adverse conditions that would kill other plants in habitat.

Absolutely agree with Dave,
also many are impatient to correct the shape cutting the stem, when it's much more better simply to give right care and wait until plant improve it's body itself...