I have started doing Ronp thing, maybe not exactly as he does....
When the pork butt gets to around 180º I put a pan under the butt on the next lower shelf. It has some apple juice, a little water, rough cut onions, you can throw in othe aromatics but right now I'm just using onions. I prefer waiting to place the pan because early on most of the drippings are fat.
Last nights smoke I ended up with about a cup of drippings I added another cup of beef broth I had in the freezer, heated it all up in to thoroughly mix, strained the onions out, and put in fridge a few hours. I then removed the fat that came to the top. Now I have a very smoky meat flavoring juice, I can added to my BBQ sauce, thin it out and use it when re-heating the pork meat, or make an original sauce. The point is this is deep smoke flavored liquid gold. If you have it, then reheating is no big deal because you can easily add flavor back in with the saved liquid.
Note, I usually have in the fridge either beef stock or pork braising liquid, the above with pork braising liquid is SO SO good.