Going from 12.5 to 15, what made you decide to do it?

Have been on 12.5 since late June, averaging 1.4lb loss a week. Never been on a particular dose this long and debating if I should ask my Dr to increase to 15. Part of me is nervous about hitting the max dosage when I might not 'need' it yet, but then part of me is wondering if I couldn't be losing more if I was already on it. What made you go up to 15? Did you wait until you were stalling or did you try to get to the max as soon as you can? Just curious on other people's expirences. Thanks!