I don't know if this topic is still of interest, but I will add my experience with the MKII Opt 002 M1.0t.
Back in 2012, I was talking with a friend who was asking me about re-capping his Acurus amp. Silly to say, but I have had my M1.0t amps since '86 and never thought about re-capping them. They have been played every week over the years and I thought they sounded just fine. (Each one in mono mode, driving a pair of AL-III+s).
That got me to searching for replacement capacitors and such and, through a convoluted Google rabbit-hole search, I ended up at Rich's CarverSite. I emailed him about upgrading my amp (which includes, obviously, replacing the electrolytics) and he gave me a typical Rich response - curt, to the point, borderline rude (IMHO, especially for a business reply) saying he had a waiting list and I had to get on it. I asked him how much for the service and got a snippy reply saying to look at his web site for pricing. I did not realize there was a separate MKII site for amp upgrades at first. Anyway, I said to myself "what a dumb-ass" and decided that no business was going to get my money AND treat me like that, so I started reading all of the info on the MKII upgrade process. I ordered enough parts to update / upgrade both amps. This was in January of 2012. The parts came in and I updated / upgraded both amps in February.
Since that time I have been working out of my house. What that means is I turn the system on at 7:00 AM (works as a wake-up call for the lady of the house) and it plays until some time in the evening, usually around 7:00 PM or so, when she turns on the TV. At least two or three times a week we stay up later and play music, at pretty impressive sound levels. On weekends we often will have marathon listening sessions that last 4 - 6 or more hours.
I can tell you that even after four hours of sustained jamming sessions, the amps are just warm to the touch. They are dead silent, they sound awesome and there is definitely more "oomph" than before the MKII Opt 002 treatment was applied.
Earlier this year I opened both amps up for a visual inspection and to check / adjust the bias settings. Both amps look perfect inside - no burned spots on the PCB, no discolorations, etc. I did re-adjust the bias on one channel of one amp (it was a bit high) but outside of that they have been played loud and hard for almost three years now and show no signs of distress. There are quite a few folks on the other site that have modded amps and I've yet to see a report of a failure or problem (other than a few amps modded by a former member who seemed to be more interested in the money than the quality of his work).
If you have a M500 or a M1.0t and it is original, it is due to be refreshed. For the small cost of the MKII upgrade, you can hardly go wrong by adding it in when you replace the electrolytic caps. Like Rich pointed out, the rest of the transistors and diodes that get replaced are of much better quality / capability than was available when these amps were new. Even if you don't bump the rail voltages up, you will have better components inside for the next 30 years of use.
WOW - Who would have thought they'd still have their amp 30 years after they bought it, still working like a beast ? Bob sure did an awesome job - it was a bucket list item for me to meet him and I finally did at Carverfest this year.
Sorry for the long post. Just thought I would share my experience.