No, I agree. He's been lurking at Hogwarts, 'educating' the impressionable young, and ... using up polyjuice.

We could get enough bits of Milland to keep Severus well-supplied with polyjuice for a good long time, but we can't guarantee Milland won't find a Protectorate embassy quickly enough to get Severus arrested if he's still playing Milland.