Growing up, I've always been told to think before I speak. I was also told to proofread before I publish! Seeing as the forums have no rule against double posting(I checked before writing this), you can address your typos in a second post, if not caught in the first 30 minutes. I also don't like the short edit time, but as a former administrator of a few other forums, I've seen what GTR8000 said plenty of times. Those folks that DO change a large portion of their post can be a real headache!
If it's just typos you're concerned about, I say don't be. Everyone is understandable, and no one is perfect. Unless your typo was WAYYYYYYY off from the word you meant, everyone probably knows what you're trying to say!