How do the merits of the Saints in Heaven operate?

> The Catholic Church teaches that saints in Heaven can no longer merit. So I was wondering **if their merits run out at some point and how that works out for them.** Related to this question, I want to know **if the saints in Heaven are elevated to higher levels of intercession(power and frequency) based on how often or how fervently they are invoked to help the saints on Earth,** this would be some kind of alternative to the system of merits when their merits would theoretically run out if they do.