That's certainly an impressive start to a running carreer... Well done!

It's generally believed that the minimum amount of runs needed to maintain the "training effect" * is 3 to 4 per week, (even if one
is a 12 miler... and
that's startling to have built up to that kind of distance in such a short time...!).
*
Simply put, the "training effect" can be thought of as your body "remembering" the runs which you do... Erm, think of your body as having a really short-term memory.
Too long between runs and your body "forgets" and the advantages that the runs provide are diluted ...
...More runs, and the body is able to remember from the "time before", thus compiling, and "adding-up" the benefits, thereby increasing your fitness.
