Yesterday, I have managed to finish up an old pet peeve of mine. I wrote a series of patches to have harness reprocess all packages, which were last checked by an older version of Lintian than the current. It is not completed to the level I would like, but it is good enough for now.
The implementation works by processing up to 1024 groups after each daily run. It also have a timer to skip this, if the run has taken more than 4 hours. Packages to be reprocessed are sorted by the version they were last processed – should a new version of Lintian be upload before all packages have been reprocessed, the oldest results are refreshed first. 
A rough estimate suggests than in about 3-4 weeks, the entire archive will have been reprocessed with Lintian 2.5.20. It is by no means faster than a full run (which is about a week), but it is automatic and removes the “human” factor in keeping Lintian results up to date.
