"But what if you don't use it for extended periods of time. For lack of a better term, can it get rusty?"

Given the chance, Strange is just going to ask so many invasive questions about Tyki's dark matter. It's interesting, he's interested, it's some new sort of power that he doesn't know much about that fuels Tyki's magic, of course he's going to try and get Tyki to explain the ins and outs of it. And, given the fact that Strange has a calculating look on his face, it's blatantly obvious to Tyki that Strange is just going to ask him so many more questions.