One question, a million answers. Personally, I do not care about LoC. When I am in a job interview, my (maybe) future boss might be interested in LoC I have written in my biggest projects. But I will never take a look at the ln# and say "Oh boy, 300 lines, time to think about splitting up this monstrosity with some smart pattern." Some concerns need 2k+ lines. Some concerns are done and fine with 5 LoC.
The important part is that you do a separation of concerns in a way which is clever, easy to grasp (for other team members or people who will have to maintain your code when you have left over 10 years ago) and fits well with the type of program environment you use (including language, compiler/interpreter, optimization,...). Also, inside each and every file, use a good structure or pattern to achive a uniform, easy to read style, which boosts overview.