24 hours is too short. I don't save passwords in my browser, I don't think a lot of people tend to, so constantly needing to re-enter the login so often gets to be quite aggravating. Some frames of reference:
Amazon - NEVER expires, only have to re-enter password if needing to look at orders or account info Facebook - Cookie logins NEVER ever ever ever expires Most phone apps - never expire, sometimes if you update an app you have to log in again Twitter, Instagram, Pinterest - I've never seen cookie logins expire, ever Most sites, if they do expire, it's at least 30 days out. Gmail is 30 days, for example, if the account is protected by 2-factor authentication, but only if it's an Apps account - all other cases I've never seen it expire on its own
Or give us the option to keep it short or forever.