A few hours of burn-in would be appropriate, IMO. 25 hours would be unecessary...also IMO, although at least one tube dealer has mentioned the necessity of 24 hour burn-in for some NOS tubes. He specifically mentioned this regarding tubes quieting down. My experience has been that extended burn-in did not mitigate tube noise.
I would question whether better sound after 25 hours is directly related to the tubes, or whether it is related to all the electronics warming up, and capacitors fully charging, etc. Of course, if all the gear is left on 24/7, then perhaps the 25 hours on the tubes is the cause.
06-11-06: Bojack
...they were not worth this kind of money when compared to other brands (Philips and Amperex) that sounded as good or better in my system.
The key words here are "in my system." The general consensus is that CCa tubes do indeed sound better in many systems, but as always, one's results may vary. Clearly yours did. Perhaps down the road in a different system that you assemble, the differences will be more evident.