I'm probably way late to the thread, but I solved the problem for the most part.
So what I had was a stock Incredible, stock battery, on Gingerbread 2.3.4 pushed by Verizon. Aside from Swype beta that was once installed (and I got sick of updating it ad infinitum), the thing was as Verizon-sanctioned as possible.
So as most people noticed, the crash and reboot-loop disease came later in the Incredible's otherwise well-functioning life. Some people think it was heat related, and some thought it was update-related.
What I found was that it was definitely heat-related, although I was unsure which component. Of course I had hoped it was the easily-replaceable battery, but several experiments with a fridge and an incubator (I work in a lab) and a piece of insulating hand towel placed between the differentially-cooled battery and phone seemed to suggest that it wasn't the battery.
My first suspicion was that perhaps the thermal management solution was somehow not working (dried-out thermal compound?). I voided my by-now-non-existent warranty by tearing into the phone and seeing how this thing was dissipating its heat. A bit to my surprise, the back of the motherboard was expected to transmit heat to the back of the AMOLED screen. There is no heatsink on the front, only Faraday cages that sat with an airgap off the tops of the chips. Some of the cages were painted dark on the inside, perhaps to better absorb IR and dissipate it to the outside.
Frankly, this was a shitty thermal management setup, so I broke out the Arctic Alumina and basically slathered these things with non-conducting, non-capcitating thermal compound.
Did this help?
Nope... or at least not well enough.
Having remember the "free" performance increase that had come from Froyo, I wondered whether the updated OS now allowed a larger CPU load with less idle cycles... and much like overclocking, the CPU had been slowly becoming less stable through the thermal cycles.
I figured, what did I have to lose?
I rooted the hell out of the thing. It was both not easy and sketchy with a high risk of bricking considering the SNAFU'ed phone. Managed to successfully get in Cyanogenmod 7.1. Still crashing, but at least no boot loop.
Played around with CPU governors and max frequencies. Ended up keeping the normal "ondemand" governor ("conservative" was sluggish), but underclocked to about 65% of its normal speed. Tweaked "backlight" (yes, I know it's AMOLED) settings and increased it to 9 steps (from the stock 5) and experimented to establish a conservative lighting profile, but actually ended up better as it was consistently soothing and readable at in all conditions.
I can now surf for nearly an hour on the thing without triggering the dreaded thermal crash. The phone is no speed demon... but at least it's back to being totally functional now.
Irony? Already got a Droid Razr Maxx on the way.
There is one lesson that I learned: root early, around when your warranty expires, and it looks like the process is stable and more-or-less worked-out.