One should definitely not be working hard. You need to minimize work and maximize income. The more you work, the less you actually make per-hour invested, if the income does not grow proportionally to surpass the current ratio. Unless you're in a good strategic position which ensures you will get huge benefits by working hard (think large stake in the company), working hard is a losing game.

A company will pay you the bare minimum it can get away with, taking into considerations all sort of parameters (such as risk of attrition) so naturally, your optimal behavior should be to work as little as possible to not get fired. Use the extra time to invest in yourself or just enjoy life.