The mindset instilled in serious poker players from the early days of the poker boom was to work on improving your hourly rate. This could be done by simply trying to play better at your current stakes, or by beating a higher stakes game. In addition, you would work on increasing the number of hands you could play per hour. In the online world you would work on increasing the number of tables you could play at once (in later days there was fast fold format poker pioneered by Full Tilt with ‘Rush’ poker or Pokerstars ‘Zoom’). A skilled multi-tabler was playing more than a thousand hands per hour.
All this was intended to improve your rate per hour. But ultimately what matters more to your bottom line than your hourly rate is how much you are able to make in your overall session(s) that day. In the online world if you were playing so many hands simultaneously (even if you were playing well and increasing your hourly) it would take a big toll on you mentally to the point that it would limit how many hours you could play effectively that day. In the live poker world you are only playing 40ish hands per hour but the mental toll comes from the higher stakes and thus bigger swings. Also, there is a physical toll of playing long live sessions.
Now that I have a family using my days efficiently is of increasing importance to me. Though my hourly is higher in the higher stakes games like 5/10nl I usually can’t plan to play as long of a session. If I lose 4 buyins at 5/10nl I will very likely need to quit the game for the night. At lower stakes I could lose 10 buyins and keep going. The length of the session would be limited only by my physical stamina. By maintaining healthy habits I could lengthen those sessions. Longer sessions means more days off which is great for work-life balance.
The paradox is that playing the higher games is necessary to build up tolerance for bigger losses and also for the experience and competition. Those games just play differently.
So while efficiency and work-life balance are very important there are other elements that need to be factored in to stay competitive.