Tubed preamps and Power amps- How old is too old???

I am currently using a Conrad Johnson Premiere LS17 preamp. This preamp was well regarded when it came out a bit over 20 years ago and list price was over $4000. It has probably seen 8000-10,000 hours of play time. The tubes are all Amperex that test and work fine.

To my ears, it sounds great. That being said, at what point either due to wear of internal parts and/or improved design, is it worth replacing? There is no doubt that things on the digital side of things have move quickly with respect to innovation and implementation but what about preamps and power amps, especially tube ones?

Any members, replaced aging tubed preamps and power amps and found it worthwhile assuming you stayed at a similar quality level? If you wanted to upgrade from my preamp, what would you consider? Budget of $7500 max. For reference, I use digital sources and an R2R Dac and Quicksilver Mid Mono Power Amps into reasonably efficient speakers. No phono section required or wanted.