I forgot that Tamiflu can be used prophylactically, although it's unclear if it helps for preventing H5N1 infections. Currently, the prophylactic dose is once per day for up to six weeks, so 120 doses would be enough for three maximum-period prophylactic courses. Well, you could take it longer, but no one's studied it carefully past six weeks yet.

But that's just based on using Tamiflu with normal flu. All the rules could go out the window with the next real pandemic flu virus.