I put my box in the trunk hoping for longer life due to less heat. I did however have an msd ignition coil go bad once after a short period of time.I've heard of them crapping after only 2 hours of drive time. Warranty covers the repairs but then it breaks again not too long after. Just never know if your going to be the unlucky person that gets a bad unit. I have the 6AL and MSD distributor on my car right now. I haven't fired up my car yet but I will soon. Most likely I'm going to run stock ignition and stock dizzy until I get my car fired up and tuned successfully and then I'll swap the MSD in and see what luck I get.
MSD sells a ton of ignition systems and there's always going to be a failure rate with any product line so who knows what the percentage of bad stuff is that's really out there. Maybe the failure rate of MSD is overhyped, I don't know but they'd be out of business if they were really that bad.