We collect all events from all relays for search (only standard kinds), so yes we store everything ever published, that's at an order of 1Tb of unique events atm. Stats only show the last 2/6 months, but they have to process everything to be correct. Stats are real time, it's a process that keeps all numbers in RAM and handles incoming events as they come.  

 Very impressive. Why store the note content though? 

 I need to serve raw data from our relay. Content isn't needed for stats atm, but it's stored.