As many others have said, you certainly don't NEED bushings to turn between centers. I turn 100% between centers, but only have bushings for the pens i do the most of. My TBC bushings look brand new after dozens of pens, mainly because tools and sandpaper have never come anywhere near them. I ONLY use them to get close to size/shape quickly. Once I'm turned down to a bit over bushings, they come off and it goes between centers for final sizing with calipers. I will say that bushings make the pen go MUCH quicker and I am much more confident turning to round and down close than without bushings (you know, it's REALLY hard to put the wood back on if you take too much off...)
But based on the mandrel bushings I have from back when I started. I would rather turn without bushings than use them. Even with my TBC Bushings, which are head and shoulders higher quality and precision than any mandrel bushings I have ever used, when I take them off and go between centers only, you can tell with the first cut that they are not perfectly concentric. It's minor enough that it likely wouldn't matter, but every little bit is one step higher...