GBLOCK413

02 TL type S 151k. Garaged. Owned car for 15 years. Battery is 3 months old. Daily driver. Twice in the past 2 weeks the battery is completely dead when trying to start. Appears to possibly be a battery drain somewhere. The first time the battery was so low the trunk release didnt even have enough power to open trunk. Jumped car and drove for 45 mins and was fined up until about 7 days later when the same problem happened. I always make sure to turn off radio, headlights, power windows etc before turning off/starting car to limit current draw at crank. Also confirmed all interior/courtesy lights are all powered off and all doors are closed. Original starter and alternator. Any idea what could be causing this? or maybe how to proceed to diagnose this issue...?