I still have not experienced a migraine attack since taking the 5-HTP (last one was sometime in July or early August I believe), but have recently been getting a few headaches again. I suspect that has more to do with neck problems I've been having though. Since I haven't been getting migraines I think the 5-HTP is still working.
Other preventative methods that I've tried in the past include feverfew, supplementing magnesium, I received a natural liquid preventative treatment from a naturopath a couple years back but honestly can't recall what it was called now. It didn't seem to have any affect though. I've also tried acupuncture, massage, osteopathy, chiropractic... most of the usual probably. Yoga, meditation, boosting antioxidants in my diet and supplementing grape seed extract, vitamin C and E etc. also to boost antioxidants - at the advice of the previously mentioned naturopath. Dietary changes - eliminating dairy products did help me a bit but I was lactose intolerant already so that could be why.
In addition to the natural approaches, I've taken prescript
ion medications to treat migraines once they happen - Migrainol, Zomig, Maxalt. They all made me feel terrible from side affects but Maxalt always worked for the migraine and allowed me to function despite still feeling pretty nasty after taking it.
I personally take NOW Brand 5-HTP with L-Tyrosine in a 200 mg dosage twice a day. I take one capsule in the morning with my breakfast and one with dinner. This is a high dosage - higher that what is typically recommended, but I've found that cutting back on it caused more headaches for me. I think it's probably different for everyone. You might want to try a lower dosage initially, especially since the 200 mg capsules can be hard to find and it might be overkill.
Good luck, please post again in a month or so if you start taking it regularly. I'd like to hear how it goes!