Using drum samples with reverb is grossly under-utilized in today’s music production. For those who do use it, a lot of it is to take the sample beyond recognition and this is incorrect usage as far best practices are concerned. Using it correctly is an art form!
The number of bars used when sequencing drum samples can vary quite a lot. Usually, the total number of bars will be equal to the length of the song as a whole, and if you’re making loops to start with, it can be a bit more complicated.
In this modern musical era, there is a lot of emphasis placed on the way snare and kick drum samples sound; specifically, whether they can cut through a mix of several different, heavy instrument tracks like strings and electric pianos. They way your samples sound in a tough mix is referred to as snap in a lot of circles. If you can get your main drum track to snap, your mix will be a lot easier to handle later, but you need to take care in your journey, as too much sound manipulation and be degrading.