Depends upon the technical dependency of the business. You start with designing the product or offering, and building a team. You end up selling to customers, administering talent, constraining budgets, allocating in investments, and briefing (educating) the management team. If you educate the rest of the management team well enough then your job should simplify dramatically over time. If you fail to do that, your job becomes worse over time, and your political power declines. https://www.quora.com/How-does-the-role-of-a-startup-CTO-change-over-time