After reading Gungnir’s reply that enemy SCV is sent to repair the bonus (Mist Opportunities) it hit me, “what is the repair rate on the bonus”?
When left alone, even a single SCV can repair the bonus to full in short time. I looked at the editor to see the repair time.
It takes 60 seconds to fully repair 2000 extraction machine. So a single SCV can repair 33.33 HP per sec
(Command Center has repair rate of 15 HP per sec).
So my advice is to destroy the bonus as quickly as possible and don’t underestimate what a single SCV can do.