sure, meditate for 50 years
Not 50 years. I once had a week long zen retreat and I went into it not at beginner level but I wasn't
that experienced either.
There were maybe 5 sessions a day, I'm not sure exactly. 45 or 60 minutes IIRC. This was combined with kinhin (walking meditation outside in a huge yard, not just walking - there was a special way to it). The rest of the time people took walks during the forest (it was in spring). We stayed in a big and very comfortable log cabin. Awesome fireplace, nice places to chill out and contemplate, lots of different sorts of tea were being had - which I must say was pretty much the best tea I ever had.
Also everybody was silent during the whole retreat except for necessary talk, practical stuff. And also sometimes a short story or koan was told at the start of meditation. There is another exception, I'll get to that.
Now my point: about halfway into the week I started getting more and more trance-like and sensory deprivation (at least deprivation of change in stimuli) like effects such as my vision becoming inverted (like a negative of a photo: black is white, white becomes black, etc). This proceeded into the following days getting more pronounced, and I started feeling like I had a gradual but significant alteration of state of consciousness. I started getting acid-like visuals but not those from a chaotic trip but instead a crystal clear trip. Or to be more precise: it started out trippy, then got stronger, then it dissolved and gave way to this crystal-clear type feeling from LSD.
There were a few private meetings with the Zen master, to discuss the development/progress or rather for guidance. I described the changes in perception and consciousness to him. He thought it was a little uncommon to have them so soon but I guess I should give my history of psychedelics use a lot of credit.
He told me in buddhism the phenomenon I experienced is called makyō: which translates to ghost cave or devil's cave. This should not be interpreted as something evil but rather illusions and tricks played on the mind in the process of some transformation. He said one must not be distracted by the trippy illusions, you must pass through it.
(I realized that LSD and other psychedelics can also have these sort of stages. At the peak there is a lot of trippiness but the last part of the plateau tends to become more 'crystal clear' feeling. My best friend and I became fans of starting with a 150-200 ug dose, then when the clear part of the trip started, take a mega redose. This seems to give the strongest clarity with relatively little 'distortion'. Conversely, when the initial dose is a mega dose there is relatively a lot mind warping. If you go even higher with both initial dose and redoses, then you can get to another level IME, where there is no more question of confusion but a feeling of being saturated with acid, feeling super liquid and dissolved into surroundings. Add sensory deprivation to that and you get a journey through imagination + reliving memories and other things.)
At the end of the week me and my best friend, who also participated, went on a long walk through the woods. I was on the verge of a ++++ and everything I saw was exceptionally beautiful and I felt deep serenity and peace from all the meditation and realizations or revelations I had during all that contemplation.
TL;DR = For me a week was enough to trip from meditation
And I disagree that this natural trip was DMT-like, more like something in between LSD and mescaline but a more pure feeling than even the purest LSD or mescaline. The reason for that seems to me to be the natural and relatively slow development, while trips tend to feel like you get more than you can integrate (what is not yet integrated during the trip must be integrated afterwards)
With meditation the integration is in realtime.