Can I pay yearly instead of monthly?

New leads are bought once, in a pack or in any number, so there is no monthly or yearly price to pick. If you already have a plan, it keeps the billing it started with, and you can see it on the Plan page in Settings.

When the leads arrive

On a yearly plan the whole year's leads go on your balance at the start: 12 times the plan's monthly number. They roll over like any other leads, so there is no rush to use them in a given month.