For this trick you will need an addon called "Recap"
Recap has a built in warning that tells you when you have too many fights stored, and it gives you a popup when you first log in telling you to clear them. So you can change this in the recap options to give you the warning even if 1 fight is in there.
So setup the warning, then in game...
as a Druid go into bear form, or as a Warrior use bloodrage, and immediately log out, (use a capital city or inn, as the logout is instant)
Then log back in, and the warning will popup saying delete all the stuff, just leave the warning up, dont click ok. You can now move about with it on, but if you notice, being in bear or using bloodrage you will be permanently stuck in combat. What this means, is when you go afk and comeback 2 or 3 hours, or even days later, you will still be logged in, because the game cannot log you out when you are in combat. It will just keep spamming the yellow message about, "warning you've been afk too long, hit the cancel to avoid being logged out"...
The nice part about doing this, is it does not require a macro program or other 3rd party program running in the background which is detectable. As your char will make little movements and jerk around on screen to stay logged in with one of those programs. With this, it just appears as you are afk, and not botting.