For what it's worth, I do the same thing and have never run into trouble in years...
...until two or three days ago.
GMail flat-out refused to let me log into two accounts (it would end up in endless redirect when I tried the second one - I quit Chrome, fully cleared cookies, history, everything... it just would not work)
It seemed to have cleared up by the following day.
That's very similar to a bug YouTube has had for a while. It may be corrected - was still an issue within the past two months - but you would get into a loop where you could not log in to YouTube.
These types of things are what I think about when people tell me how great the Google programmers are, but that's another topic.
...until two or three days ago.
GMail flat-out refused to let me log into two accounts (it would end up in endless redirect when I tried the second one - I quit Chrome, fully cleared cookies, history, everything... it just would not work)
It seemed to have cleared up by the following day.