The Agency Numbers list has a Health column showing outbound health for each number. Use it to spot numbers that are starting to degrade and rest or retire them before the drop shows up in your campaign stats.
Where to Find It
Go to Call Routing → Numbers. The Health column appears alongside Number Name, Number List, Assigned To, and Status.
How to Use It
Watch for numbers whose health is declining, not only ones already failing.
Rest a degrading number by pulling it from active rotation for a while, or retire it and buy a replacement.
Keep enough healthy local numbers in each pool for the area codes you dial, so resting one number does not leave an area code uncovered.