'Not too often' is important.
Yes and no... It's more dose dependent, IMO... People tend to intentionally "overdose" with psychs, so that they feel inebriated (like with other drugs)... A strong blotter of acid turns most people into gibbering idiots and they learn nothing, regardless of their usage frequency.
I've seen many, many people go backwards - spiritually / emotionally / functionally - with psychedelics...
It's more common for people to go backwards than it is to go forwards.
This doesn't only apply to repeat users.
Over the decades, I've seen many people have single trips that totally derail their sanity for prolonged periods of time.
Most psychedelic users aren't interested in growth, from my observations.
Your average psychedelic user isn't exactly enlightened...
Just go to rave to confirm this.
In the end, I think, you get out of an experience what you want to get out of it.
I find methamphetamine and dissociatives to be comparably mind-opening.
Hangovers are great, too. (But not alcohol.)
Sobriety, I think, can have as much potential... but I'm not quite there yet.