From Cyclomatic complexity (Wikipedia):
The cyclomatic complexity of a section of source code is the count of the number of linearly independent paths through the source code.
I recommend that you keep that number under 10 in a single method. If it gets to 10, then it's time to re-factor.
There are tools that can evaluate your code and give you a cyclomatic complexity number.
You should strive to integrate these tools into your build pipeline.
Don't literally chase a method size, but try to look at its complexity and responsibilities. If it has more than one responsibility, then it's probably a good idea to re-factor. If its cyclomatic complexity increases, then it's probably time to re-factor.
I'm fairly certain there are other tools that give you similar feedback, but I didn't have a chance to look into this yet.
