Best practice for instance variables and uninstall

Hi,

I just added support for multiblock in the http://drupal.org/project/taxonomy_nco module. I just passed around the multiblock instance id and inserted this id in each variable the block was using. So I now have variables in this form:
taxonomy_nco'.$multi_id.'_include_tags_in_related
taxonomy_nco'.$multi_id.'_minimum_match_intersection
taxonomy_nco'.$multi_id.'_default_minimum_match_nco
taxonomy_nco_block'.$multi_id.'_vocabularies

Is there a "best practice" to deal with uninstalling a multiblock-enabled module? Is there a way to ask "multiblock" what are the initialized ids ? Or is it better to run a dbselect on variable and remove every variable matching the pattern? I guess this second one is better because we don't have a way to be notified by multiblock when instances are removed and their variables will live forever (or do we have this? also: does multiblock notifies block owners when multiblock is uninstalled?)

Thank you for any hint.