I'm on my 6th and 7th (6th live, 7th RGH)
7th is my first RGH console, 6th was to replace the 5th, 5th replaced the 4th, 4th, 3rd, 3rd, 2nd, 2nd, 1st
Never had the RRoD just some crap about volition of the ToS
you cant erase all the cache if the title update is being stored in the game data storage, where you'll find your save games too.
(ie. Official Dashboard > Settings > System > Storage > Hard Drive > Games and Apps > (Game Name) > Title Update)
Cache was used for a long time, newer games use ([game id]/000b000/[title updates])instead of cache.
If you have the game for the live console, load it and see if it prompts you for a title update, if yes, take it, then copy it to your USB then copy that to your RGH...Simple really.
Or just manually get it from http://marketplace.jqe360.com/