Infact, I teach my students that we increase depth (and thus experience) by 1 ata at a time. Initially, this doesnt seem to be much, 200- 235 isnt a major step, but 235- 270 focuses the mind a bit more, then 270- 300 really brings some issues to play that are easily masked by shallower dives and 300- 330 makes all of the world of difference in terms of planning, complexity, logistics, safety, contingencies etc. Why choose one deco model over another? What are the implications for ICDS, how do we accommodate that? And much more- these things are real and the lessons highly pertinrnt at 300+' in a way that iThus these students are well and truly set up for significant trimix dives when they leave my instruction- they have been there and done it, rather than merely read about it and dived to the minimum of 250' depending upon agency. The difference is too great to risk, in my opinion.
So as always- seek out an instructor who has experience and who knows what he/ she is doing. and Train Right!