He's not using stale data. He's using the PQ to get the caches into GSAK, then using the api to periodically refresh them. He's missing caches because they have funny placed dates. The problem is that you can only set a date period for a PQ back to 1988. Presumably, no caches listed on the site have been place prior to that. The field is configurable by the cache owner, however, so it can basically be any date. Some people use strange dates as part of their puzzle, or a clue, or they just think that they'll be cute.
As it is, I'm not sure that his solution is feasible as I don't believe that they have been tracking publish dates and the information is probably not in the db. There has never been a "publish date" in the GPX and it sure isn't in the api. Everything is based on "placed date".
Thanks for your input, if the published data is not in the db, then the only option left for Groundspeak is to not allow placed dates before current date.
I think I will continue to only run pg's for new caches and then now and then run all my pg's for older dates. I will always miss the caches with dates before the possible search from date in the PG, but anyway there are plenty of caches out there;-)