I got an 05 Mastiff, my first EHC was changed under a TSB within the first year, though the orginal was fine. The improved EHC was in for a few years but then one day while doing maintenance and waterproofing the connectors with Di-electric silicon, I jammed a pin and broke the one from the EHC for the Oil Pressure idiot light, so replaced it when the EHC were somewaht cheap (just over $300 then). That one last for another couple of years but got shorted out due to chaffed power harnes issue, put the second one back on with the non-functioning Oil Pressure light. It went for a good year until I decided to upgrade to the BDPP PDM to be on the safe side since BDM was no longer around and BDPP had a new option.
Changed my whole system out using the PDM (which I do not think is available for the 04 and earlier models, but not sure on that or if they are working on one or not). The PDM was a breeze, seems to work fine and has features I like. The kit included not only the brain (PDM) but new wiring harness and even battery tray. Was able to save the ole EHC and harnes in case the PDM does fail or to pass to some member in desperate need that I may know.
Bottom line, to the best of my knowledge, even though I had 3 EHC, none of them failed due to EHC (one was upgrade, one I broke and the thrid got shorted due to harness). Have close to 30k on the bike, it is 7 years old, never hesitated to go for a ride be it short or multi day. A few times over 500 mile days easily. I expect long life and many happy miles with the PDM, other have gone the WP route and from best gather information, majority seem happy. I prefered the PDM-we will see!
Learn to wrench and do the work yourself and bascially get it right, keep it maintained and ride the SOB and enjoy the miles, do not worry about the possiblity of being stranded anymore than one would be with a 3 year old car and having a battery go south. If it happens, get it back home and fix it and then ride some more. Wrenching and unexpected adventure are part of the culture, be it the unexpected torential rain storm, snow dusting, love bug swarm, kettle heat, flat tire, dead battery or broken electrical. Frustrating all, but part of the adventure and for the most part once one gets over it and back on the road, the feeling and the memories cannot be replaced. That is part of the biker culture be it on a BD, Honda, MTM, Duc, Kawaii or a Vespa, enjoy the ride!!!!