I have also looked up a few on IMDB and it seems that many "contract" actors must have been working with few breaks. 10+ movies per year for some of them.
In the days of the contract actors, acting was a job, just like any other job. Actors were paid a reasonable salary and were expected to work full time. It was not like today, where a big name actor makes more on one movie than most of us will make in our lifetime. Today, the top actors can make one movie per year and still make more money than 99% of the US population.
Another big difference is that in the days of the contract actors, very few movies were filmed "on location". The actors showed up for work at the same studio every day, put in a days work, and then went home (or out partying). When one movie was done, they started the next movie. Being a movie star prior to 1952 was much more like being a television star today.