36 hours, jeez, that's a lot of time to set aside, or a long time to be so "altered." LSD seems plenty long enough, and has a well-established safety profile when used with care. DMT might be a bit too quick, like a drag race, but I'd think an Indy 500-type duration would be enough for most people, rather than going up to a whole 24 hour endurance race like LeMans.
Something producing a full-on LSD-like experience in say, 2-4 hours would be a huge hit, both with psychonauts and scientists. I think 8+ hours of a psychedelic experience can be extremely exhausting, and long enough to forget a lot of the desirable details. To each his own of course, and a marathon can produce an extreme feeling of accomplishment for those willing to endure it. I just think something more manageable could be more useful, and become more accepted.