Technical debt is an inevitable side effect of legacy code. Some code can (and should) be pruned, but institutional memory fades—what if there's a reason certain lines were included that may not be immediately obvious? Done right, unit tests can serve as documentation. Later on, these tests can illuminate what the developer was thinking when they created the code.
If you are unsure about the things you should be doing to control technical debt in your existing performance test suites, here are a few questions that should be considered. Asking yourself these questions regularly will go a long way toward keeping your tests fit and sustainable and helping control a few common factors that lead to technical debt in performance tests.