Refresh token expired within 4 hours. How I can create long term refresh token?

Hello, community

I used OAuth2 authentication and get refresh token but my refresh token expired within 4 hours. How I can create long term refresh token to generate a new access token and use REST API for future use? 

If I create access token before 4 hours then it returns new refresh token that also expired within 4 hours. So suger CRM granting long term refresh token?