I think this depends a very great deal on what your personal definition of a 'short burst' is. I know some people who will overwork themselves for weeks, then burn out and be unable to leave bed for weeks; this seems bad.
On the other hand, when I hyperfocus on something for several hours and then take the rest of the day off, I know I get significantly more and better work done than when I sort of idle away for sixteen hours, half-working and half-scrolling-Twitter.
I'm not sure why cycles on the scale of weeks seem much worse to me than cycles on the scale of hours, but one hypothesis I have is that it's about avoiding the lows going below a certain threshold. If I work very hard and am tired and hungry afterwards, that's fine; I'll rest and recover. If I ever reach a state where I'm too tired and hungry to be able to cook a good meal and go through some bedtime rituals, then I'll stop eating/sleeping properly. Once you hit a local minimum, you can be trapped there in a vicious cycle where you don't have the energy to take care of yourself properly, and you don't have any energy because you aren't taking care of yourself properly. Big highs & big lows are fine so long as you can recover from the big low and get another big high, but above a certain threshold you can't dig yourself out of certain holes without help.
If longer stretches of peak productivity produce worse burnout, then perhaps the key is keeping those stretches short enough that the burnout doesn't cross that threshold?
Thanks! And there's theoretical reasons my prior would be on steady work (including some HN or SO or book comment I saw (maybe related to personal slack?) claiming that 40% was the optimal capacity to work ourselves at in general, due to task throughput concerns)