One can always do ones own modding, the version of sh3 i run is heavily custom modded for my personal use.
Anyhow guys lets stick to the topic and keep the flames down
As for myself i often do drills to add to my own sense of immersion. typicaly a shallow dive, then a crash dive followed by going deep to make sure everythings screwed on tight. Then ill typicaly blow tanks to make sure its working right, and usualy end off with deck and flak drills. Ill also check fuel consumption and see how she handles, and i dont run SH3 commander with (or without) the sabotage thing.
I like doing it as it enhances my gameplay experience.