Etizolam has a ceiling - THAT is why in some nations it wasn't as strictly controlled as other 1,4-benzodiazepines.
When I was young and stupid(er) I consumed 500mh of the stuff (we were sent 600mg for instrumental analysis and one only needs circa 1000mg so we had spare). I remember taking it, doing some work, walking out of my home, into town, took a package to the postoffice, saw a friend and stopped for coffee, walked back home and went on with my day.
It's supposed to have anti-depressant activity and a few wise heads who know these things inform me that to get the best out of etizolam you need to take it for weeks. Now I wasn't depressed - just curious to know if that ceiling was a hard ceiling or a soft ceiling. It was the former.
BTW Just because I did something dumb and got away with it is of zero statistical value in knowing if YOU would likewise be so lucky. Who knows? That ceiling MAY be subject to genetic variability so for some people it's lower, some it's higher, some it may not exist. In which case I imagine 500mg would be a lot.
For comparison 500mg of payrazolam saw me sleep for five days and not be out of it until day eight or nine. It's an extremely safe benzodiazepine with an even larger TI than diazepam... but evidently no ceiling.