Do you ever trade the 3rd monthly?

When the 1st monthly is about to expire, there's a "gray area" of 1-3 days where the 2nd monthly has less than 30 DTE and the 3rd monthly has more than 60 DTE.  So in that case, you can bend the 30-60 DTE guideline and go with either the 2nd or the 3rd monthly.

However, you'll find that the 3rd monthly won't have as good liquidity as the 2nd monthly. So you'll probably end up trading the 2nd monthly even though it has slightly less than 29 DTE. But if you manage to get filled on the 3rd monthly, then good for you, and the liquidity will improve once the 1st monthly actually expires.