Obviously this is something that you need to work through with your doctor.  The following is from my experiences with these medications.
 
1200mg Lithium Carbonate, 720mg Verapamil and 12mg Melatonin have been my daily core meds./dosages for more than a decade.   As symptoms change (increase/decrease in severity and frequency) I adjust dosages accordingly.  I’m typically at the levels mentioned above 70% of the time and able to decrease to lower dosages the remainder of the time.  It’s a constant effort to find the lowest yet most effective dosage levels/schedules for treating existing symptoms.

Success…, absolutely, without these preventatives I would most likely be a very exhausted basket case.  Results are far from perfect, breakthroughs are common.  However, I gain a significant level of control over the disorder through these drugs.  My indicator to their effectiveness is those rare times that I forget a dose or miss my schedule by more than an hour.  Increased symptoms/severity is nearly immediate and it sometimes takes days for CH to return to more controlled levels.

Like most meds. used in treating CH, there are a lot of things to look out for.  Most are commonly and easily recognized side-effects, others should be monitored through routine tests (EKG/ECG, blood tests).  A significant amount of detailed prescription drug information can be obtained from Multimedia File Viewing and Clickable Links are available for Registered Members only!!  You need to or to establish the basis for treatment/monitoring discussions with your doctor.

Best Wishes,
burnt-toast
(Tom) 

I've had clusters for 18 yrs past 9 chronic, I have been on verapamil 480, Topamax 125 and lithium 600 for years. Have a few breakthroughs, nothing too bad keep O2 handy. Side effects are mostly from the topamax but anything is better than a cluster!