If you increased it from 15 minutes to 60 minutes, you'll still be logged out. It'll just be after 60 minutes have gone by, not 15 minutes. However, to prevent being logged out, check the "Remember Me?" box when logging in.
Ah. So if I didn't check "Remember Me?" when logging in here on XenForo Community, if the tab was selected and 60 minutes passed, I would appear logged out only after refreshing the page or visiting another page, but if I were on another tab and 60 minutes passed, I would appear logged out when going back to the XenForo Community tab?