When the trip ended, I wondered to myself "if the effects were cumulative or if there would be tolerance"
Answer: definitely cumulative!
I've read that it exhibits a reverse tolerance, which I would definitely agree with. So the more you consume, the less you need to achieve the same result. I've never consumed any concentrated extracts (just "1X" leaf, I suppose) and after my experiences with it (especially in light of the reverse-tolerance effect) I have absolutely no interest in taking a concentrated dose (even a "mere" 2X).
And once developed, it doesn't seem to wear off. I measure the time between my salvia experiences in years, and even after I hadn't smoked any for ~8 years, it only took about a half to two-thirds as much to get to the same place I got to all those years before (which was outside the Universe after I fell through a black hole), and it was loaded from the exact same old stash of straight leaf. So the potency lasts a long time, too.
I once berated some dipshit clerk working at a smoke shop through my friend's phone (on speaker) when my friend called me from the shop for advice about some stuff he was getting ready to buy. When I realized what was going on, I was mostly diplomatic and tried to inform the clerk of the error of his ways and not dog-cuss him or insult his intelligence; not sure it made any difference but if we don't take care of our own scene by addressing ignorance and negligence when we encounter it then the legal climate surrounding it will never relax.
Anyway, my friend had remembered a story I'd told of a crazy experience I'd had and he wanted to see if what he was buying was the right stuff. The clerk only told him that it was a "high-quality, legal herbal product" or some such lawyer-speak (gee, thanks for being so helpful and informative! With clearly-inexperienced customers being sent out the door as poorly-informed as that about what is gram-for-gram the most potent plant hallucinogen known to man, it's no wonder it got banned in so many places, grrr...).
When he read the package to me, it turned out to be a bag of 50X Salvia concentrate. "Wait, uh... did you just say 50?!?"
FWIW, my friend was NOT into the kinds of deep, hyper-intense psychedelic experiences that can change who we think we are in an instant that feels like a lifetime (or vice-versa). Quite the opposite; he likes to drop a 5-strip of blotter and go to a big football game with 100,000+ other people while occasionally listening to the Dead on his headphones (he's not a particularly close friend, lol). A 50X Salvia trip may well have flipped his shit permanently, and/or left him with a raging case of PTSD. He very well could have tried it during a football game (the horror...). I mean hey, it's legal!
Giving people like that those kinds of drugs without properly informing them about what to expect is every bit as bad as slipping someone a drug without their knowledge or consent. I know a couple who instantly and permanently severed all ties with a longtime friend of many years after he'd loaded them both a massive bong hit of "legal weed" that turned out to be 10X Salvia. The asshole then proceeded to laugh his ass off at them as they writhed around on the couch and mumbled incoherently (after suddenly being paralyzed by an overwhelming degree of visceral terror that they never saw coming).
Salvia flips my shit pretty hard even at 1X strength, and I know what to expect and consciously embrace it once every 5-10 years or so but I sure as hell wouldn't want to get taken by surprise by it and can't imagine how traumatic it was for that couple.
All that said, I still greatly value the perspective my experiences with it have given me, but in a way that's similar to how I feel about a number of highly-educational near-death experiences I've had. I mean the "Holy shit, I almost just got killed! I'll never sneak up behind a grizzly bear and slap it on the ass before running away ever again!" kind of educational near-death experience, not the "I died on the operating table for a few minutes and saw the Light but I came back!" kind.