So far I've only tested this in Civilization II and Interstate '76, but the results are consistent with both:
Whether sitting in a menu or playing the game, recompiler blocks are constantly being created, removed, and sometimes evicted.
I'm not an expert on caches; however, this seems strange to me. Is it possible that it is re-creating blocks that it had previously removed or evicted? Or is it self-modifying code trashing the cache?