Switching from low KD keywords to high KD keywords

Hey I was wondering if I optimize a service page for let’s say “small business accountant chicago” because it has a low KD (hypothetically speaking) under the URL “/accountant-chicago” would it make sense to change the content on the page on a later date when the site in general and url specifically is more authoritative and optimize the existing page for “accountant chicago” rather than the long tail version? If not, why and what’s the best strategy to tackle the situation?