What is the expiry of SAML Refresh token , generated as Part of Apigee Edge SAML OAuth2 support?

[#1]

curl -H "Content-Type:application/x-www-form-urlencoded;charset=utf-8"-H "Accept: application/json;charset=utf-8"-H "Authorization: Basic ZWRnZWNsaTplZGdlY2xpc2VjcmV0"-X POST https://login.apigee.com/oauth/token?mfa_token=<6 Digit token> -d 'username=jdoe@example.com&password=abc123&grant_type=password'