I have owned the original 5D, a MKIII and now the MKIV.

I often leave the camera untouched in its bag for some weeks at a time and never before the MKIV have I pulled the camera from the bag and found a battery completely flat.

When I put it away the battery was at 100% but when I took the MKIV from its bag yesterday and turned it on and it was completely flat. This was with the LP-E6N.

Not sure exactly how long it was in the bag but I only bought it in August this year and would have spent weeks playing with it before I put it back in its bag.

I'm quite fussy with batteries and it would have fully charged before putting it away so even giving it the benefit of the doubt I am guessing would have been packed away for @12 weeks max with GPS set to Mode 2, Every Minute and GPS logging disabled.

Definitely harder on batteries than its predecessors IMHO...