I have no numbers or anything resembling a controlled experiment but the ambient temperature in my apartment seems to affect boot times on my Trinity board. The colder it is from roughly 70°F the longer it appears to take. Warmer temps don't seem to have the same affect but it could all just be in my head. The two Jaspers I've installed Coolrunners into boot in less than a minute on average. One is less than 30 seconds without fail and the other takes up to two minutes with the rare boot time beyond that. The sole Falcon seems to have good boot times. Not a one of these three is well optimized for the RGH install and it was more "well it works, let's seal it up" type install. I don't normally do RGH installs so I never had any incentive to try to optimize these things.
CR3 Pro allows much easier tweaking. My brothers slim that was 1-15 minutes is now no longer than a stock console.