The expectations can be pretty stable, but because they cover so much of the system, they tend to be more fragile. End to end tests are also often flakier becau

The expectations can be pretty stable, but because they cover so much of the system, they tend to be more fragile. End to end tests are also often flakier because they're dealing with the system at levels meant for human interaction, like by driving actual browsers. Because they encompass so much, they're also the slowest. When you have a problem with an end-to-end test, they can take way more time to debug because of that. So I'd agree with them; E2E tests are the hardest to maintain.