chinchillas

Question
How long does a female chinchilla have to stay with its mate?

Answer
I assume you mean how long does it take to get pregnant.  Females can get pregnant once a month but many females prefer to bond with their mate before breeding.  I have had many couples take as much as a year to produce their first litter.  Once she is pregnant its best to leave them together until delivery.  At that point you can remove the male to prevent her getting pregnant again right away.  If you plan to put them back together be sure to place the male's cage right beside of hers so they can still see and smell each other.