What Performance Budgets Actually Buy You
A budget is not a target you hit once. It is the conversation you get to have before the regression ships.
Teams usually adopt a performance budget after a bad quarter, treat it as a one-off cleanup, and quietly drop it once the numbers look fine again.
The budget is a review tool
Its value is not the number. It is that a pull request which crosses the line gets a discussion instead of a merge, while the change is still small enough to argue about.
Pick numbers you are willing to defend
A budget nobody is prepared to block a release over is documentation, not a budget. Fewer limits, seriously enforced, beat a long list everyone overrides.