You know what? A good way to determine these kinds of things is to look at what is recommended in your nation. I presume every nation has its own recommendation regarding the adequate amount of vitamin B12 that one must consume daily. I feel that it depends on your age. For instance, my adult cousin brother consumes about 2.4 micrograms of it daily. He is in the US, and he takes that much of it as per something called the Recommended Dietary Allowance. I do not know how much it would be in your nation, so it may be best to check the related information.
 
I do not feel that it is unsafe to go above the daily recommended quantity of it. I also do not think that you must take that much of it daily.