The ends should be sealed very shortly after it's cut. I do it right away... 2 or 3 coats of shellac within the first hour.
When it comes to splitting osage logs, you have a little leeway. You can split them right on the spot where they fell, which often makes them easier to get out of the woods and/or load... or you can bring the logs home and spit them there. They'll be ok for a while in log form, I've let the go for a month or so, but they won't begin to dry inside until they're split.