I've kept ponderosa pines alive on the east coast the last two and a half years without any problems. With mine, I've cleared out a lot of the muck in the first spring after arrival and they seem to be quite vigorous after it. I think with the rain and humidity I have in my area, as well as my watering habits, keeping a tree in its native soil is a recipe for disaster.
That being said, I think some have had success in my area leaving the tree as is for a few seasons. However, I lost a really nice douglas fir that I got in a fall workshop the following June. It could have died for other reasons, but when I pulled it out of the pot, the root mass was in a solid brick that wasn't well aerated and seemed filled with dead roots. That experience, along with seeing how poorly the roots of field grown trees are in original field soil, have made me lean towards a first repot as soon as I can.
So, I now try to clean a big portion of the rootball the first spring after the tree arrives, slowly working the native soil with tweezers and chopsticks and not cutting any roots. It can take a long time to do this, so I have a water spray bottle nearby to keep the roots moist as I work. I do not completely bare root, nor do I use a hose on the root ball. I also let the tree rest with no styling that year, and feed and water pretty heavily.
Just remember when you repot to tie the tree down very securely into the pot, especially if you might be putting in heavy bends in the future.