Depending on the lube you use, you might get some corrosion on the brass where the lube touches it if it sits for a long time.   I've had that happen when I made my own lube, but not since switching to DGL.

I've shot lots of ammo that's a year old, and some older.  Generally left over ammo from matches, and it's always shot just as well as when freshly made.

If you are worried about it, prep the cases, and load the primers and powder with a wad on top.   Then just before going to the range, compress the charge if desired, and seat the bullets.  The powder and primers will last longer than we will, with no degradation.

I hope that's useful to you.

Chris.

I have had no problems with storing loaded BP ammunition. No corrosion, no failure to fire. I use a combo of SPG and DGL for lube.

I have shot five year old Swiss BP cases lubed with Alberta Schuetzen Lube without corrosion occurring or any affect to accuracy of the loads.

They were stored inside in my basement.

I know that loaded rounds stored outside can have the brass become brittle and crack on firing. 
Over extended periods of extreme winter and summer temperature changes the brass becomes brittle.
A fellow provided me loaded cases that had been stored more than 10 years this way in his unheated garage.
1 out of every 5 ruptured when fired.

The longest I have stored loaded BP cartridges is about 18 months, not by choice, but no problems....

What happens to BP when it's in a sealed cartridge for years? Has anyone pulled bullets and seen something that made them think it went bad at a set period of time?
I've also fired BP cartridges I knew were many decades old and not had any issues I could tell. I didn't chronograph them as I was trying to just use them up to get cases to reload with. But they seemed to shoot fine, and groups weren't erratic.