The best answer to this is to consult your prescribing physician. I would think just offhand that you won't start all over again, but it probably won't be the 3 month window you would have had left. You might be on it for like 4 months or so but it depends on how bad your acne has gotten...
Lo dose isotretinoin works very well for seborrhea and desultory acne breakouts. A 40mg/d dosing is more along the lines of the Full Court Press, where we are looking at a 5-7m course of treatment as a definitive therapy. Lo dose is adjusted by the patient as needed. I usually dose at 10mg...
This is a high dose of accutane. If you are not getting results, consider other factors for your acne.
Dairy products, a high glycemic diet, hormonal imbalances, makeups - all can contribute to acne. Discuss these with your doctor.