Does virtuous detachment usually separate and cause blindness?

Rarely: Usually just causes some floaters. Sometimes can lead to retinal detachment.

Not usually: Vitreous detachment happens to all of us, eventually. The great majority of the time it does not cause problems. In the very small majority of patients it can cause a retinal tear or detachment. If you are experiencing symptoms such as flashing light or new floaters, you should see an eye doctor as soon as possible