0.7mg per day should be fine, 0.5mg to 1mg should have a very similar result as far as some study's portray. I'm on 0.5mg and have only been on finasteride for 5 days (wanted to start small and go up to 1mg if I don't have any obvious side efects within the initial month).
My view is that if your hair loss is really aggressive then take the full 1mg per day but if it's fairly slow (not much loss per year) then 0.5 or more per day should be fine. Like I said 0.5mg upwards is fairly flat in terms of response.
I would say as long as you are getting ~1mg per dose you should get the benefits of taking finasteride. I keep it simple and just get and take 1mg pills, but have cut 5mg into fourths in the past. Whatever works for you.
As you can see in finasteride's DHT conversion inhibition curve, even 0.2 mg provides only 7% less inhibition compared to 1 mg. 0.7 mg will more than suffice.
I just choose to take 1 mg because I can't be arsed cutting pills and my insurance covers it anyway so I wouldn't save money by splitting pills regardless.