I think the boom and bust idea is wrong, as illustrated by the studies
@ME/CFS Skeptic describes in this article which show that there is not an inherently different behaviour pattern practiced by pwME when not in PEM compared to healthy controls.
However, I don’t think that means the term many of us prefer, push and crash, is wrong. My understanding of push and crash is that every day there is a limit on how much exertion I can do without triggering PEM. I don't think it's something I can predict, as so many factors influence it such as quality of rest and sleep, sensory input, my current ME severity and exertion over previous days and weeks, and the cumulative effects of all exertions .
If I push past that elusive boundary today, I am likely to sleep badly 'tired but wired' and wake up the next day feeling totally crap, much sicker and much less able to function, and the crash/PEM is will last days or longer unpredictably.
Which is a longwinded way of saying that, usually with the benefit of hindsight, I can see that I have pushed and crashed.
When my ME was mild and I was still working, my activity patterns were, if anything, less erratic than before I got sick, in that I quickly found I had to cut out the 'boom' days such as strenuous days hiking or evenings dancing. My activity pattern was much more evenly spread by necessity.
Except when I pushed a bit for an hour a day, a week, probably barely registering as different from variation in a sedentary healthy person, but resulting in a crash/PEM that kept me off work and much less active for a week or more, some or all of that week confined to bed.
I think if a study were to be done over a year instead of a week it would find, not boom and bust, but a pretty even level of exertion that had fluctuations caused by unavoidable activity increases dictated by events, and other variations maybe related to symptom variation with causes unrelated to exertion, and life in general.
Superimposed on that overall pattern, for a pwME there would be episodes of PEM, showing up as very significant drops in activity for a day or more, and recorded by the pwME as feeling much sicker.
What I think needs researching is whether these PEM episodes are linked in a measurable way to a change in activity pattern over preceding days. I think mine generally is. So for me the push-crash idea is correct, but boom-bust is not.
A further thought. I watch a bit of sport. Tennis players and road cyclists who 'boom' to the level of total exhaustion one day, and return for more day after day, notably cannot do this every day. They are described as suffering exhaustion after a 2 week tournament or 3 week race and need some rest days during the event, so they can't compete every day or week of the year. In fact a perfect example of a boom and bust lifestyle. Yet they don't have ME/CFS.
