Don't put it off.
I repeat, do not put it off.
I went yesterday to get a post in the root canal I had last month, my crown will be ready in two weeks. I had to have this root canal because I put off going. If you wait, it will only get more painful and more expensive. I went from having a broken filling, which then broke down more to the pulp, which became infected and went down into the root. If I had waited any longer it would have caused an abscess, as it was I had a temperature running a degree higher from my infection.
Fixing the filling would have run a couple hundred, but since I needed a root canal, a post and a crown, it ended up costing over $1000. It's the only one I've needed though, and I'll never need (or want) another root canal. They suck big time.
Sometimes before I sleep, I can still feel the dentist scraping the root out of my molar with a metal pin.