I noticed the same thing for IE8.
I have had automatic browser forum log-in working for many months as long as it was the same day. But recently I have noticed it also works the day after. This is very nice! The only negative I think of is that I might forget my password after weeks and months with automatic browser login (but should it happen, I am sure it is easy to get help)
It's even working for Chrome. And yes this is nice.
Oops, I forgot to mention that I only use Chrome when visiting Tableau websites