...That vivid memory illustrates another aspect of the problem: just as lab hours per calendar day (and perhaps also hours worked alone) are at their highest, one’s own experience is nowhere near at its peak. Graduate school is where chemists encounter a lot of reagents and procedures for the first time, and not all of these encounters will go smoothly. This is when one might find out, for example, just how remarkably air-sensitive trimethylaluminium is (if there isn’t a flame burning from the end of the syringe needle, the bottle has probably gone off), or just how long a large aqueous phosphorus oxychloride workup can sit around before it suddenly erupts all over the inside of a fume hood (several hours, damn it all)....I'm reminded an episode of one of my favorite old shows "The Unit", where the youngest operator on the team grazes a senior operator in the arm during a training exercise. After giving Bob a thorough razzing, they congratulate him on reaching his "200th hour"* where he has "enough experience to be confident, enough to screw up real good."
It is a funny aspect of graduate school in chemistry where you're the least experienced, you work the most hours that you'll probably work during one's time in research chemistry and you're likely to be the least supervised you'll ever be (if you continue onto industrial bench chemistry.)
*Apparently this is flying terminology?