As soon as everything stabilizes, specially temperature, you are good to go. Every system is going to fail some test if you let it go for long enough.
Personally, I view them only as troubleshooting tool, not a definite proof that all's well and peachy.
Doing it too often, for too long may just over stress system needlessly. Running usual tasks is greater proof of good working system. OS and programs may fail because of many other errors, not only because of HW.