I've read here and elsewhere it SEEMS it's best to do whatever mega dosing you are planning over the course of any day...NOT ALL AT ONCE.. IF you have any asorbtion problem if you just spread out those 1000 doses if you even GET 10% into your system, that's good! If it were B-6 I'd balk, being a victim of 'value addeds' that mean nothing... But, excess B-12 just simply leaves you with no harm done...Soo like Vitamin C, it doesn't hurt anything but can't hurt just to have it there IF it can be taken in...
I surely hope this all helps!