Tesla CEO and founder Elon Musk has advice for prospective buyers hoping their vehicles will be future-proof: Shop elsewhere.

Musk made the comment when responding to a Twitter question about the possibility of a paid upgrade path for existing vehicle owners who want the new sensors, computer and other components now shipping in so-called ‘HW2’-equipped Teslas. He also gave us some insight into the pace with which Tesla will be significantly revising the tech offered on existing models — big changes will come every year or year-and-a-half, on average.

Tesla will never stop innovating. People are buying the wrong car if they expect this. There will be major revs every 12 to 18 months. — Elon Musk (@elonmusk) January 22, 2017

That’s definitely a more aggressive upgrade pace than you can expect from models offered by traditional automakers like GM, Ford and Toyota. Typically cars remain relatively static in their basic design for up to half a decade, acquiring new options and small features, but certainly not seeing “major revs” that can make the difference between enabling self-driving and not, as is the case with the HW1 and HW2 Model S and X.

This might rub some Tesla owners the wrong way; a Tesla is a huge investment, and seeing significant model revisions at a pace similar in frequency to how smartphones are updated can be frustrating. But as Musk notes, it’s a trade-off Tesla is willing to make in order to push the envelope in innovation.

If we applied resources to doing super complex retrofits, our pace of innovation would drop dramatically — Elon Musk (@elonmusk) January 22, 2017

Musk also noted that retrofitting older cars with HW2 kit would require extremely complicated and basically involve stripping the car to its frame, plus replacing over 300 parts. Focusing on updating existing cars would also impede Tesla’s ability to create and improve new tech, he added.

The bottom line is that Tesla is a very different kind of car company from what consumers are used to, and that extends to their development cycle. To some extent, future-proofing is always partly actually handcuffing yourself to the past, and the trajectory Musk envisions for Tesla doesn’t allow for much in the way of standing still, even in the interest of helping customers feel like they’re getting more value out of their investment.

I think Tesla’s ability to compete with established industry leaders actually depends on adopting the revision paving of a tech company first, so it’s good to see Musk commit to substantial changes at such a fast clip.