How long does it take for an ovarian cyst to go away?

My friend has multiple cysts they are pretty small the doc gave her birth control pills im aware they dont get rid of them the pills jus prevents more to create and it prevents you from ovulating so it mantains your hormones from not going crazy which is what makes the cysts. So am wondering has any women ever expirienced having ovarian cyst non-cancerous and not mistaken by a tumor and no surgery needed, how long did it take for the cyst to go away on its own? Ive read they do go away but how long does it take because am aware they painful and am worried for my friend. Thanks