Always logged in - not working

[#1]

When I open my laptop in the morning, my first (or second) port of call is the Plusnet forum.... and I always check the box,..... always logged in....
until recently, this remained the case, when I closed the forum, did other things, and came back to it....
just lately, this seems to have changed, when, if I leave the forum open on some thread.... go away to do something and then come back... I do a "refresh" to see what has been going on, and any new posts.... and I have to log in again.... so....
Always logged in?  Not working..........

[#2]

Cookies being deleted?

[#3]

Erm/////  no..... I don`t delete any cookies between my sessions.... like I said.... I look at the forum. post if necessary, leave it open...go away, and a couple of hours later... got to log in when I refresh the page...
I could understand it, if I logged out, or closed the page... (but prior to this, I used to close the page and then come back and was still "Logged In". on the same day....
Mostly I use ccleaner at the close of day... (around midnite)... but then I expect to Log In.... the next time after using CCleaner.) 

[#4]

OK. it now seems to be working ok....
just logged in.... read a few posts..... exit the page. and then came back in via the bookmark.... still logged in.