Historically, crests were often (although not always) intended to import additional meanings and intonations - sometimes they were more playful than the arms as such (serving as funny mascots for the tournament games), sometimes they were more "collective" (this was not uncommon in Scotland where the idea of a crest was interlaced with the idea of a badge) or more "particular", etc. The tournaments, jousts and melees at one side, and the rigid fixation in armorials and on monuments were the poles between which the tradition of crests was fluctuating. There were no strong general rules, and that the early treatises did not impose their putting-in-order authority upon the crests, this could be rather a reflection of the common views than the reason for the said freedom.
As all we do understand, "German heraldry" is a generalisation. And as far as we accept this generalisation, we mostly meet arms of respectable, well-established families kept unchanged in all lines and branches, provided that no quartering was added and no augmentation was granted, and as far as the artists involved were able to avoid mistakes.
However the opposite examples are numerous, now as a reflection of the armigers’ socially unstable standing, and now as a part of a proud noble representation. Obviously the lands by the Rhine were particularly prone to the Western influence in general and the idea of heraldic cadency in particular. There is the famous example of a Swiss-German family von Eptingen, whith the coat shared by all the family members and with distinctive crests galore.
and here as well (below):
I have to ask Michael, is this scan/image of the left hand page of an Roll of Arms? I ask based on the orientation of the crests and the reversal of the Arms, I assume that this is to show "respect" to the right hand page?
Dear Jeff, yes, this was done out of the heraldic courtesy. Here is another page therefrom: