Currently, VerifyBeforeExit flag is ON for debug and fastdebug builds. This flag has a potential for slowing down VM upon exit, in some cases considerably, e.g. when a lot of OOPs are allocated. In other cases it is needed to find/diagnose issues, e.g. in certain stress tests.

Since nightly/PIT/Promotion testing primarily execute on fastdebug builds, this flag may have a considerable impact on testing performance.
Please study this impact, and consider disabling the flag by default, and enabling it in tests on a case-by-case basis.