If you don't seal the ends immediately, they will get drying checks in the ends that will continue to run deeper and deeper into your staves, which you don't want to happen.
If you don't split the logs, they will not dry, but rather, they'll ultimately split themselves... and not where you want them to. You don't want THAT to happen either.
If after you split them into pieces 4" or so wide across the bark, you don't soon reduce them by taking off the bark and sapwood and then seal their backs, they can split down the sides to the point of worthlessness... more cracks you definitely don't want to see.
So yes, you need to get busy and take care of your bow wood.
I HIGHLY recommend you go buy Dean Torges' book 'Hunting the Osage Bow' TODAY... and follow his instructions. It's all in there. This is the only piece of instruction I had in my hands when I began building selfbows and my first bow, and second, and third... still shoot to this day.
link to Hunting the Osage Bow All the best in your quest!