Butt time in the cooler

They should be good for 5-6 hrs if wrapped tightly.

This is not a good indicator. Again, the surface temp of the meat and ambient temps in the cooler are your concern, not the interior of the meat. The bacteria are going to be present on the surface of the meat, not inside it (unless you are cooking boneless butts or did multiple injections, etc which could introduce the exterior bacteria to the interior of the meat).

Keep an eye on the surface temp of your meat. Once it hits 140* you are back in the danger zone - in theory at least. In my personal opinion (backed only by my own research and no empirical data) the danger is far less with a smoked butt. Why - because you have smoked it (creating an environment and surface area prohibitive to bacteria growth), you used a rub that presumably had a certain amount of salt content (creating an environment and surface area prohibitive to bacteria growth), and you exceeded the temp of 140° for at least 10-12 hours then immediately wrapped the butt in foil. Where would the new bacteria be introduced that could begin growing? It isn't on the foil because bacteria cannot survive (the ones we are worried about anyway) in an environment free from water.

I've left two butts in a cooler covered with towels and newspaper and after 7 or 8 hours I still had surface meat temps north of 150*. This is all just food for thought. Just use your own opinion and common sense and you'll be fine. The longer you wait to pull the meat the less your risk of bacterial growth and problems.

Thank you. It really is common sense for the most part. I can't take credit for all of this -- most of my opinion and knowledge on the subject come from information gathered from folks here. Even those that post what I believe to be incorrect information have forced me to research their responses, further educating myself on the subject.