There is not much relation between what type of developer you are and your work life balance. I am a Full-Stack developer and I have a proper work life balance. I start of at 2:30PM and work till 5AM or 5:30 PM, just like all other FrontEnd and BackEnd developers. In Agile environment, I will take up FE card today and a BE card tomorrow. FrontEnd developer will take FE card today, tomorrow and day after. BackEnd developer will take BE card today tomorrow until he become a Full-Stack developer. This is the only difference. Just because I know more technologies or languages doesn’t mean that I need to work harder or more.