I'm sure you can experiment, but whynot just do it every other day rather than every 3rd day?
Some things to keep in mind:
- Half life of finasteride is 6 hours (figure out how much is left in your blood at your next dose)
- Response curve is about flat above 0.2mg
- Some response from as little as 0.01mg
- Half life of Type 1 5AR is 14 days, for Type 2 5AR is 30 days. (Don't ask me why, but I'm pretty certain this doesn't mean you can take one pill every week or so and be as good as EOD or ED).