They drying time will vary due to the number of peppers, the humidity and pretty much any other factor, so keep checking them. Over drying the peppers is not really a problem.
First picture is what they look like when they are done. They are crispy and break apart. Note the darker color. Peppers like this will pretty much last forever.
If you decide to leave the stems on some, just put them in a closed container. The Thai Dragons are used in many hot Oriental dishes. These are hot enough that they can be used over and over again. Toss them in with stir fry and let them season the dish. Remove then when done cooking, rinse them off and let they dry out again before storing for the next use.
After drying these, I put them in the food processor (note that this is OUTSIDE). The first time I did this in the kitchen, we had to evacuate the kitchen for the next 3-4 hours until the dust settled.
I prefer a bit courser grind, so I use the pulse switch on the food processor until they are broken down to what I like. Be careful when opening the lid, as the dust alone can kick your butt (does a wonderful job of loosening any clogged sinuses.)