As previously noted, there isn't much movement when going from 25/06 to 6.5/06. For that mater even .270 to 6.5 isn't much. Long story short, unless your loading for a bench gun just load your most accurate, safe load and fire at will. From that load forward I neck size and trim as / if needed until the primer pocket gets loose, the neck splits or the body gets thin at the case head when checked between loadings. I normally get 7 to 9 loads from the Winchester 270 cases I use in my 6.5/06. I load the 140 A-max and the 142 SMK and don't go beyond anything published in the bullet manufacturer's manual.
That being said. I have fire formed cases though in the past. Both 25/06 and 270 cases. I used 9g of Unique. Filling the case to the top with COW and capping it with canning wax compressing the COW to the neck / shoulder junction. I was hoping to extend the case life and save a bullet. It does save using a bullet, so if your preparing 100 to 200 cases it maybe worth it. The once fired case has shown me some improved accuracy, but not a ton. I get .750 to 1.0 MOA with full length sized new brass and .5 to .6 MOA with once fired neck sized brass. As you can see both loads are going to go where you steer them, and could ethically be used to hunt deer sized critters out to 300m+ with confidence. As usual the shooter is the weakest link in the equation especially off hand. Your mileage may vary...
