Youre fine,
2 years ago I ended season w/ one unfilled ML tag. I had a clean barrel and took the primer out. I left the BH209 charge in and locked the gun away. Pulled it out the next season for to go to the range and the charge from the year before fired normal, hit the 100yd target exactly where I left it the last t ime it fired.
** this wasn't an accident, I left it intentionally to see if it would work. I had it locked virtually the entire spring/summer and knew it had a charge in it the whole time. I have a hunting partner that shoots smokeless out of his savage and is having to reload his charge almost within a couple days if he doesn't shoot at an animal. Been telling him to just shoot BH209 (he can shoot either out of his ML) as it seems to be alot more stable and certainly has better longevity than just a day or two.