XF 1.4 Members being logged out....

This may be as easy as a simple tick box I can't find. We have quite a few members who are saying they have to log in 10 times a day, each time they revisit. They say they are ticking the "stay logged in" box. Hoping this is an easy fix. I searched the forums & saw some people use an addon, prefer not to use more addons. Thanks for any help :)