65-80 for readability however once you introduce indentation this naturally increases. I always felt that shorter lines were a good way to encourage less nested code. Alas after all these years the consensus is against me.
There is more difficulty working with code such as
if x { //... } else { //... }
Than code like
if x { // returns from this block } // execution continues
In some legacy code I sometimes encounter very long chains of checks which nest 4-8 layers, which becomes very difficult to maintain a mental model of where you are in execution at any point. I try to refactor into the second pattern from above when possible.