Why would you wait?
Seriously, I don't know why people ask that kind of question when there are things you should be doing as soon as you can be doing them.
If I told you that you could wait 6 months to start probate it would be rather foolish for you to wait 6 months to start probate when you should be starting it as soon as possible after the person died.
If you are asking because somebody who should have started probate didn't start it, then you should say so. Details count. The more details you give the better the answers you will get.