How to break in a tube preamp?

Please excuse me if this is a stupid question.
I want to break in a newer ARC tube preamp (ARC says 400-600 hours needed to run in new Teflon coupling caps, etc.) and am wondering if I can accomplish this without running my tube amp at the same time and avoid spent KT-120 power tube use. Can I only leave a digital source on repeat with the preamp on and actually "burn in" the unit or is that not fully running what needs to be run to accomplish "proper run in".
Just enjoy music as you normally would. That way you can hear if the sound changes any. Don't get in a mindset that it will sound bad if you don't burn-in first.
That would be ok to do. I have never bothered doing this and just played new equipment and enjoyed. Never heard much change in sound except for my Lowther speakers. Don't obsess about breakin. Just listen and enjoy. You won't be disappointed
To some extent, so-called "break in" is the listener becoming accustom to the new sound. That part requires listening to the system, so just do that and don't worry about break in.
While I appreciate what you are saying, I was wondering electrically if this would help the break in process or be a waste of time without the signal running through the amp as well. I don't plan to leave it run for 600 hours, but I would like to let it run for likely a few days to assist the process if it makes sense electrically.
Should work fine to not power on amps, but they do need to be connected to your preamp. I've done this.
In the case of my Modwright LS100 I was told by Dan Wright that the caps etc in his require same length burn in as yours and that I need to play music, not just have it on
If it makes you feel better and you think that the "break-in" time is needed then do it as you described. I would listen every night and let it run the rest of the time with the cd player on repeat and the amp off. The main point is that you enjoy your new ARC Pre and the process of listening and upgrading your componets.

Provide a review in a few weeks.
As long as your preamp is on and connected to your amp(s), your amp(s) don't need to be on.
I recently purchased a Modwright Ls100 which has the same break-in period as your amp and was told by Dan Wright that I needed to play music for the caps etc to properly break-in, versus just leaving the amp on. Unlike Ahendler's experience I have noticed a significant difference in this amp as it continues to get "mileage"
Breaking in your preamp does not require that your power amp be on. Just do what you said--connect your digital gear to the preamp, put it on infinite repeat, turn your preamp on and use your regular volume setting. The preamp has a loading resistor on its output (to prevent any DC from building up if there isn't an amp connected), so running the CD player and preamp in this fashion is fully equivalent to listening to music through the entire system.
Thank you everyone for your input. Much appreciated.
I am looking forward to hearing the post burn in period. By all accounts the teflon caps are wonderful once they have considerable time on the clock.
OH thats a tough one!!
I own a linestage with teflon caps, but i would never say that they are universally good--it is all a matter of voicing. A cap that works well in one design, and to one person's taste can be really bad sounding in another application. I've heard gear "upgraded' with Blackgates and teflon caps that sounded really bad. I know of people that search for fifty year old caps that sound great in certain designs (another linestage I own uses these kinds of caps).

There really isn't such a thing as good caps and bad caps, it is more the case of finding the right cap.
Based on my experience, my recipe for the best:

You don't need the amp on but you want a source playing music going thru the pre. I also believe in cycling the pre (during this time), ie, on all morning/off for a few hours/on late afternoon-evening/off all night til the next morning.

Two of my CJ preamps have teflon caps (ART 3 and ACT 2.2). I liked them out of the box, really liked them after a few hundred hrs, loved them around 6 months (have no idea the hrs at this point), and have been "in love" with them from a year on. They just seem to get better with time.

Enjoy the trip.