Well ,after many mails I got BAV final answer today...How surprising...A big NO.
In other words,their PR and customer service is pure BS,we are alone with any problem we'll have.
Check you sea cocks and valves regularly they are NOT marine grade and will sooner or later let you down.
Me,on next out haul will change them all to proper Bronze.
The subject of seacocks has been extensively covered in the yachting press recently, particularly Yachting Monthly, because of concern over the standard required to meet the RCD. This sets a minimum service life of 5 years which is easily achieved with unsuitable brass valves and fittings. There have been some failures with these fittings - more the tails and other fittings rather than the valves themselves, but despite pressure there is no plan to upgrade the specification. If it is any consolation the same poor quality valves are fitted to most production boats, including the expensive Scandinavian boats, so it is not a Bavaria unique problem and other builders have also been subject to the same criticism.
One of the reasons why it does not become a bigger issue than it could be is that most valves are not permanently under water and are usually remote from any other metal fittings. The one that usually goes is the toilet outlet as it is well below the waterline, as is the inlet. The only one I have replaced on my 2001 boat is the toilet outlet, because it was seized rather than suffering from corrosion. Handles are always a problem with rust, but it is very difficult to source DZR valves with stainless handles.
So, not a very satisfactory state of affairs, but doubt given the background you would get any joy with the manufacturer, just as other people have had no luck with other builders. Given the literally 10's of 000's of these valves in use there has been no epidemic of boats sinking through failure. Better quality valves are not expensive in relation to the value of your boat, so best to just replace them if you are concerned about them.