Due to the late hour, it might be awhile before more knowlegable folks see this. I can give you some rookie insight and you can wait it out for others to respond.
Assuming you want to make pulled pork from the butts, you need to get them to an IT of about 205. That is real close to your cook temp of 225. That will extend your cook time abit. Most times, things seem to slow down as the approach the ambient temp. No real data to support this, just observations. Look at it this way if the IT is 180 and smoker temp is 225, you are applying a relative heat of 45 degrees to raise the IT. At 200 IT you are applying 25 degrees.
Then you have something called "the stall" to complicate matters. As water evaporates it carries heat with it. This is especially evident on larger pieces of meat. You eventually reach a sweet spot where the steam coming out of the meat and the heat you are applying reach an equalibrium and "stall" the rising temp. Eventually the meat gives up enough vapor it can no longer stall the cook and the IT will begin to rise again.
Alot of people power thru this by wrapping the Butts in foil when it reaches the stall. This seals the vapors (steam) in and takes advantage of it to help cook the meat.
You mention several thermometers. One wonders how you are reading them. If you are opening the door to check temps, you just let all the heat out and added probably 30-45 mins to your cook EACH TIME. I did this on my first smoked chicken and took nearly 4 hrs to do what should have been a 1 1/2 to 2 hr cook. For this reason, most of us have remote therms with wired probes to monitor IT and sometimes smoker temps too.
All this combined with the pure mass of food to soak up all the heat you are throwing at it, I would really recommend cooking at 275 or so.