At least one situation comes to mind where it might happen: If I wanted
to publish a collection of HOWTOs, e.g., from the LDP. If every one of
them included front and back cover texts, that'd be a mountain.
There is no difficulty at all here. This collection would be an
aggregate, and here's what the GFDL says about that:
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document's Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.
The first alternative would apply here, so each document could have
its own "covers". Nothing is cumulative for the whole collection.
I made an effort to find and resolve such cumulation issues while
revising the GFDL for version 1.2.
