The therapeutic index of chloroquine in the treatment of covid-19 is relatively high. Some people take chloroquine or hydroxychloroquine at about half the acute dosage used for covid-19 (autoimmune disorders) for literal years.

Given the half life as you mentioned, once or twice a week with enough lead time would be a sufficient dosage against covid-19 too. It's just that if you want to reach the concentration of chloroquine that you would have to take it over a long time otherwise, you need very high doses. And since you're already infected and have a ton of the virus, you also need higher concentrations than for prophylaxis.