cat in heat...a few questions

[cherry_darling]

i have a 7 year old female cat, who is almost always in heat. i've had full intention of getting her fixed for awhile now, but every time i have the extra money something else comes up so i'm not able to get it done.

lately, the cat has been in heat for 2-3 weeks at a time, & it's been driving me crazy. she's also been peeing on everything, & i don't know if getting her fixed will help that. are the two related at all?

also, i did something stupid & let the cat out a few days ago. it was a dumb thing to do, i know, especially since she's an indoor cat, but after not sleeping for a few weeks, my nerves were gone & i couldn't handle it anymore. it's been almost two days & she hasn't come back. she has been outside before, but never for more than a few days. i've heard that cats in heat can be outside for a week, even. but i'm just worried that something will happen to her. does anyone have any experience with a cat being in heat getting outside? how long are they usually gone?