The traditional CS flows a low amount of air ,which can leave a very damp cabinet environment.
In some cases,with larger loads,the meat can look and feel like it is wet.It can prevent you from developing bark-which can be a major flavor layer.Heavy rubs can feel like wet sawdust.
Experience will teach you.Yes,opening the door can extend cook time.That may be the way you learn what is going on and gain your own cooking experience.As to extending time-so?We aren't frying an egg,so we just build it into our schedule.
No,I'm not advocating opening the door constantly to just play with the meat all night,but it can teach us when it is beneficial.
Also,you may cook at different temps and decide to use the moisture as a tool of your cooking.
Ribs can be wet with no external color and a wet mouthfeel with no "bbq" flavor.
If cooking on a long,oilpipe horizontal cooker with offset firebox that flows a lot of air,I might be using a garden type pump up sprayer to drench the meat every 15 mins and must open the door.
I think you will find few CS cooks that need to mop or spray,unless it is to add a specific flavor layer.