Longer stem, need to re-cable?
I went from a 60mm to a 100mm stem and there was no need to re-route the cables. As pointed out in the comments (thank you all for the comments!), this is not general and it really depends on how much cable there is. Fortunately in my case, there was enough.

On a related note, I had to add a spacer on top of the stem, because the new stem is lower than the one I had beforehand.