Cheers fellas, my question is now, does my wallet.dat backup become invalid after each occurrence in which my node is used?
I would say, your backup becomes incomplete each time the key-pool is enlarged AND new addresses got some coins in them.
Never checked it in code but assume the XC qt also has a key pool of 100, maybe Dan can comment on that.
https://en.bitcoin.it/wiki/Key_poolA discussion about this issue can be found here:
https://bitcointalk.org/index.php?topic=1414.0I start mine with a large --keypool parameter to be sure i got a lot of addresses prepaired and included in my backup