How long does anyone keep Lydia around and how often do you use her?
Is there anything gained by letting her go ?

I never use Lydia. She's quite useless as a follower.

I've never used her... I like Argis the Bulwork. He's a man that can smite whatever I can with the same ease

Lydia sits in my home all day and eats my bread.

You get satisfaction from killing her. In fact if you've obtained a better follower, you'll get money for killing her.

I've only used that woman, can't remember her name, whom I defeated in battle of fists.
She's red haired, steel plated and kinda heavy...

Never. She is an awful companion.

A couple of my characters have used her as a follower. I've kept her, off and on, for about 15 lvl's after that I find another follower. I like Argis and Erik, though I refuse to give any follower an area effect staff or scroll.

If on PC and able to use the UFO mod she is quite nice to have around. The mod even changes the voice actress to something less asinine.

If not, not so much.

Uthergerd the Unbangable

Lydia's ok as a follower, and actually very strong if you level her. A problem with her is that people get her at a low level, and since followers haven't levelled with the player as they should - rumored to have been fixed by patch 1.6 - she seems weak when the player outlevel (is that a word?) her.

I can't stand her, though, the way she sounds so sarcastic and seems to smirk at me all the time. Last I had her with me I put a helmet on her so I didn't have to see her face, that made her a little less annoying. And she stalks the bedroom at Breezehome - can I have some privacy, please?!
So getting rid of Lydia before purchasing Breezehome is my number one concern when I get her.

Exactly.

She any good?

She's doing fine walking with me so far.

I kept Lydia around through my first character's entire career. I devoted http://www.gamesas.com/topic/1344810-lydia-if-you-dont-keep-up-im-going-to-leave-you-somewhere-in-a-dark-cave-underground-where-the-spiders-are-going-to-eat-your-brains/, but still I kept her around.

they're all useless.

where can i get another follower? i'm on 360 by the way

She's good for awkwardly watching me sleep in Breezehome. *shudder*

I don't think I have ever used Lydia. No particular reason for that other than I usually already have a follower or I don't do any of the main quest after 'Unbroken'. I might use her at one point, but I don't think I will any time soon. I much prefer Jenassa.

EDIT:

LOL

Lydia: 'I am sworrrrn to carry your burdens"

Makes me hate her more and more each time I have to listen to that. I swear an Elcor has more enthusiasm in it's tone of voice than her.

Where is "Spell Book: Shut Lydia's Mouth'' when we need it most?

I kind of like her, she helped me alot the beginning of the game but has with most followers i rely heavily on stealh or i die very quickly, lydia either causes a good distraction or alerts every hostile in the area. I made her full daedric so she can take the hits but i find it alot easier to leave her and take a more stealthy follower (need a cushion when your a vampire )

Depends. Do you want a mage, a thief, a ranger, or a warrior?

Look in the inns, meaning the inns in the large cities. I think there's a mercenary available in Whiterun and all the other large cities. Each large city has (I think) a quest where you can become Thane of that city, entitling you to buy a house and have a Housecarl from that city.