When that feed is removed from abnib, yes. In fact, I’ve already implemented it. =o)
When they drop off the end of the feed; tougher, and I don’t want to. But I feel that I’ll be respecting the fact that it has been removed by not making it internet-accessible: it’s just like keeping copies of old RSS on my home PC. Nonetheless, in the longer term I’ll probably end up setting up an auto-culler to wipe the oldest crap at any given time.