In my 15+ years of web development, there are very few things I can say are unequivocally a good idea. It almost always does depend. Storing timestamps instead of booleans, however, is one of those things I can go out on a limb and say it doesn’t really depend all that much. You might as well timestamp it. There are pl...
Using a nullable Boolean to represent 3 distinct states just adds confusion and complexity to your system. In most cases I would prefer to use an enum with 3 fields which is non nullable.