I meant Lithium Manganese lol. I currently use three LSD LMD batteries for my nodes, which gives me around 6Ah. The self discharge is rated at 10%/yr. My testnode is running for weeks now. I use scheduled transmits to control the power consumption. The MCU sleeps and only wakes up to increment a counter when external interrupts are triggered. Every 15 minutes the RTC wakes the unit up to perform some analog readings and to send a message containing the counters and the analog values.
Li-SOCl2 batteries are also very interesting, they have a self discharge of less than 3%/year, in a lot of cases outlasting the lifetime of the device they're in . But they are expensive, around €24 for 3AH.