I'm quite certain that you are talking about something different. You say you never got any real benefits from your vibrations and that it is hard to sustain for longer than a minute. In my case, this experience isn't something I induce but one that happens for more than 3/4 of the day. It stops if I feel a strong emotion, and may I have remember to remember to get it going again but just feeling the emotion reminds me. The best part is that when it flows, it completely rids me of that emotion and I feel great.
When I was spending my meditations opening the kundalini, I could have reported the same sensations as you. I found however, that with time the vibrations became much faster than I had anticipated. One night while watching television, I realised that I was vibrating more powerfully than before at my heart level, this caused quite a bit of internal pressure which I conciously released. The vibration then shot up to the top of my scalp where it was again released and the instant I did so, my awareness expanded in a enormous way through a full 360 degrees, and for the first time in my life, I woke up. I was having an experience of conciousness, which I now know your yoga friend would call samadhi. It felt as if a light bulb had been lit up in the centre of my head and that I had a halo. I actually had what felt like a halo! I realised that the vibration was always there, I had just been taught to block it out, but now I vibrated the same way in which a guitar string will vibrate when the same note is hit on a nearby instrument. My body became like an antenna and conciousness no longer had to be forced, but was gratefully received.
After such experiences, the ego does come back but has a weaker grip and most begin to systematically hack away at the unnecessary thinking and stressing because they now have a very definite goal. Ever since then I have no choice in the matter, my body vibrates as does the world around me, and life is infinitely more satisfying.
Maybe I had some form of neurological damage or something, but I later learned that my experience was quite a common one, especially amongst those who do yoga. Even if this whole enlightenment idea is a load of crap, it sure as hell makes life more interesting.
The yogis and enlightened masters of the past intimate that not every person who has opened the kundalini is awakened, but every person who has ever been awakened has opened it, or it has opened because they woke up. Remember if you THINK you're in the moment, you're actually a fraction of a second in the past.
Sticks n stones'll break my bones, but if I land the first one, you're in trouble!