I forgot where I left her...do they return to your house if they are your housecarl? I'm so annoyed running into every town and every doorway.

^Bump^

if you are on PC you can use the console commands to move her to you or you to her. I believe followers do eventually return to their default location, but it maybe based on the follower in question. I know Meeko the dog returns to his shack, the only follower I have really had.

Ahhh, wouldn't it be nice if the follower showed up as a little blip on the map? Anyway, I believe after three in-game days, you'll get a message saying something to the effect of "So-and-So got tired of waiting and returned home".

The Thanes will go back to your house. Don't know about any of the others.

Please don't bump threads with "bump" posts.

Yes, your companion will eventually get tired of waiting and you will get a message "Your companion has gotten tired of waiting and returned home" or something similar. If the companion was Lydia, for example, she will eventually either show up at your house in Whiterun, if you own it, or if you don't, in the hall at Dragonsreach. Other companions will return to where ever you met them or hired them.

my bad, but thank you for the knowledge

After awhile they will just return to where you first found him or her..