I've had a year of productive work thrown away by a clueless and arrogant founder that didn't understand the product he was trying to build and the market and was blaming everyone but himself. So you can have the crazy overtime and the bad management that waste it all.

It's not really a question of big and small. Most companies are badly managed (or I am very unlucky). I found in big companies they at least know that making basic efforts to keep employees happy is profitable long-term.