When should you consider ephemeral environments?

ive been seeing more talk about ephemeral environments lately, especially for CI/CD and testing. the idea of spinning up a fresh environment for every branch or PR seems really slick for consistency. but im wondering about the practicalities. what's the tipping point where the overhead of managing dynamic environments starts to outweigh the benefits? are there specific types of projects or teams that benefit most? curious to hear what others think about when this becomes a good fit.