If it's not a general problem, I will advice you take a look at your security settings on the site, maybe you have set it to automatically logout after a certain time period online, I know of several sites with this security feature where one can choose to be automatically logged out every 2 hours or 3 hours so he or she can log in back with the password, this helps in times when you are online and maybe slept off, your account can't be access just by anyone since it will log it self out, you can check ascertain if this is the problem.
I agree with the previous suggestion to check your security settings. Most platforms allow session duration management. How about a password manager? They can securely store and automatically log you in. You could get security and convenience.
Finally, try BetFury's customer service. You're probably not alone. They'll appreciate your reporting a bug.