I'm a bit of a different case, have been volunteering/working at retreat centers in Peru and Mexico for the last 6 years (and am somewhat of an apprentice in a particular tradition).

There are tough parts physically sure, you mostly get used to those parts, sometimes I'll have long stretches of not vomiting and sometimes it'll be every (or multiple times per) ceremony.

As far as "finding out new things", we often use this analogy of layers of an onion (of which you tend to cry more with each layer coming off :)). Breaks between sessions to integrate are needed- after a retreat you might find that some of your baselines have shifted, and you need to find your new normal (or make changes in your life to break out of the old patterns you didn't realize you were stuck in because it was just normal/programmed and not a choice previously). After you've adjusted/integrated other things may begin to surface that were just overshadowed by the energies you've cleaned up before. (A good shaman has cleaned themself to the point that their own energies no longer dominate their vision, and they can "see" outside themselves to diagnose/heal others). Anyways sometimes the physical side effects are just too much for some people and it's understandably not the modality for them...if you spend your ceremonies being entirely consumed by those effects, you can still make progress drinking with a good shaman (though it might be a few ceremonies before you get your head above water).

I still get surprised (especially with master plant diets). Ayahuasca isn't addictive but I think for some of us there is an intellectual addiction to it. The scary ones are the ones I look forward to now :).

I'm very biased but I'd only recommend doing retreats that offer master plant diets in a traditional Shipibo context if you're looking to make lasting changes. The master plants (adjunct plants taken alongside ayahuasca) offer a whole other dimension that ayahuasca alone doesn't even scratch the surface of. A weekend retreat in someone's garage might be ok for a "tuneup" or to see where you're at once in a while, but it's not the place for deep work or for someone new imo (and you risk opening a box that you won't have time to wrap your head around).