I've had to switch to the harder but more brittle, street gears too as Pro Gears in 3.73 (lower numerically than 4:10) are no longer available for a Dana 60. I have only done a dozen passes on them but I intend to inspect every season. I footbrake BTW (best 60ft is now a 1.29), a good 9" type rear is on the list for the future.
Below is a Dana 4:10 street gear which had around 120 passes before they let go, about 90% of the teeth were like this and the discoloration on the breaks pointed towards an inclination to believe that they may have been cracked for some time.
The issue with the transbrake is the backlash isn't taken up throughout the drive train, like it can be on a footbrake and this adds to the "shock" on the rear gear as the backlash is taken up. The Soft pro gears give a little but the caveat is they wear quicker. How quickly will depend on driving style and how well they were set up, the whine will let you know when they need replacing