I suspect most Bavaria owners are staying silent on this matter because there is not really that much of an issue.
I have a year 2000 34 and this year changed the original toilet seacock as it was showing minor signs of turning pink and going brittle so your 7 years sounds a bit pessimistic.
Certainly though with Bavaria you get what you pay for and must expect some cost savings along the line and it’s not as if other production boat builders all stick to bronze.
I have a much bigger concern with pitting on the lower sail drive and at £4K for a new one fitted would be chuffed to bits if I only had to replace the other brass seacock!
Then of course there’s the usual corroded exhaust muffler which is quite common on Bavaria’s and I won’t even mention the Eberspacer I had on an earlier Bav. Fortunately I now have a Mikuni which is more silent, easier to service and doesn’t have a habit of breaking down every time you really need it.