Funny (hilarious, even) that you mention caffeine because the other day I drank a couple of cups of preeeeetty strong coffee in the mid afternoon - the company was excellent, btw - and around 17.30 I followed it up with a 3½ gram rue brew. The effects of the rue were splendid, there seemed to be no downsides to the preceding coffee intake (but just you wait!)
Most evenings I round things off before bed (at least, when it turns out to be an evening where I
do manage to go to bed) with a cup of herb tea specially formulated by me, for me, to take care of various effects of me being me. Now, it could be that some of those herbs turned out to be less than helpful, or it could just have been the combination of everything with everything else (not to mention the maca and ashwaganda that I put in my even snack of oats)... but...
Suffice to say, I did not get one single wink of sleep the entire night after going to bed at 22:30. And this of all nights being the one night so far in the entire year where I needed to get up promptly at 5:15 and turn up on time for a job. In lieu of sleep, I at least managed to meditate. The bit where the ashwaganda kicked in on top of the hemp flower tea was predictably pleasant - and this was after the rue had definitely worn off. (I typically get about 6 hours out of my usual rue dose, this one went on for about 8 hours, perhaps not only because of the coffee but also because I had thrown the new seeds in with the previous day's already-thrice-brewed seeds.)
When it became clear that I most likely was not going to sleep at all, I spent a while considering if there was any possible way I could phone the guy up and say that I wasn't able to come and work with him after all. In reality that was out of the question - he had asked me because he needed someone at short notice.
After waiting a fair while for the alarm to go off, once it finally happened I jumped up and had a cold shower, got myself breakfasted and generally as sorted as I could given the circumstances and went off to work. I stayed out from six in the morning until nine at night, working a solid twelve hours in between not counting journey time and had a great time. Now the guy wants to hire me on a regular basis
All in all, it's hard to say whether this counts as a cautionary tale or not, but I wouldn't recommend attempting it as a long term strategy. It would be pretty much guaranteed to go horribly pear-shaped.
Interestingly perhaps, I got through a gruelling workday without any coffee at all and was all the better for it.
“There is a way of manipulating matter and energy so as to produce what modern scientists call 'a field of force'. The field acts on the observer and puts him in a privileged position vis-à-vis the universe. From this position he has access to the realities which are ordinarily hidden from us by time and space, matter and energy. This is what we call the Great Work."
― Jacques Bergier, quoting Fulcanelli