> Since we cannot make exact predictions it’s better to make methods as small as possible instead

No, please don't. Separate your functions based on what they're doing, not an arbitrary line count. If it takes 50 lines to do what's necessary, a 50 line function is absolutely fine.

You know what isn't fine? One operation split into 50 different subroutines that are all useless on their own unless composed together in order.

Make your interfaces small, not your functions.