Binnesman,
This will be my first post on this site, but man do I love smoking Pork Shoulders. Your plan to cook at 210 to 225 will have that 8 plus pound shoulder taken 15 to 20 hours to cook. Pork Shoulders can handle the higher heat. If you want to start the morning of and get it started 5 am ish (and that is the smoker is set, ready to go, meat prepped, and on the smoke around 5 am) and have it ready for a 5 pm dinner, then you want to keep your smoker at minimum temps of 275 to 300. You will want to make sure you foil wrap at 160 ish and once wrapped you will want to turn the heat up above 300, between 300 and 325 and let it go until 190 to195 and start to see if it is probe tender. This method has consistently placed my cook times between 8 and 10 hours (with one taking less and one taken more time). Quick note on Pork Shoulder tenderness, you may be worried that you will pull it too late and it will dry out, but actually if you pull to early it will still be tough because you need that time and temps for the fat to breakdown into goodness. It is that fat being fully broken down that gives pulled pork it's "juiciness" and "tenderness".
If you want to keep your smoke at lower temps, I think you will want to plan an over night cook start about 20 to 24 hours before the goal of dinner. Even if you go this route I still would not have the smoker any lower than 225, shooting for 235 with a window of 10 degrees plus or minus (i.e. 225 to 245) for me is as low as I will go.
If you have a cooler with towels, a Pork Shoulder can stay in that thing hot for HOURS!!! So I always air on the side of being done early rather than pushing it too close.
If you have heard and read all about this next item please disregard, but also make sure you are ready for the stall. The stall happens around that 160 internal temp mark and this is when you have cooked the meat to the point where it can start to break that fat down. If you are cooking at 225 that stall is going to be significantly longer and I mean significantly long than if you are cooking at a higher temp and/or if you wrap. The higher heat and the foil speed up this process tremendously. Make sure you are ready for this both in the time management and psychological. I know this seems funny, but you will be there and the cook will be going good and then it hits 161 and has only moved to 164 in 3 hours what is wrong?!?!?!?! Nothing! And even though I know this is coming, it still can freak me out, and makes me think something is wrong. Again, foil and higher heat greatly lessens this experience, but it is at it peak when cooking at 225!
Now make sure to keep some leftovers for yourself for the next day, because I 100% agree pulled pork is absolutely better the day(s) after it has been smoked.
Good Luck,
Mike