What? A month at least? O_o
Hm, so why should it be a mistake to take Severus with him? What would be the difference to what they have now? I mean, Harry has to work here and there so they will only see each other in the evenings - which, as far as I understood, they are doing already. So, yeah, why not follow his gut instinct? It seems to have done him good so far. :)

Also wanted to say that I love the little domestic scenes with Hermione and Ron.