When to try a new medication?

How do you know when it is time to switch to a new medication? I currently take two seizure medications, but after 3 years on this combination, my simple partial seizures are getting much more frequent and more intense. They are very mild but happen in clusters just about every day, and of course there is always the possibility that the partial seizure could develop into a generalized seizure (which has happened with me, but very rarely).

The seizures started to get worse about 6 months ago, and my doctor recommended weaning off one of my medications and adding zonegran. (Another reason we had talked about switching is that I am having memory and focus issues on one of my current medications.) I thought it over all summer and into October and haven't made a decision. I've made an effort to get 30 min more of sleep every night for the past 4 months (even though it's still not enough, to be honest), but I don't think it has helped. I don't run anymore because I have seizures more frequently when I'm exercising, and I don't like that I've had to give up a healthy habit. I've been on many different medications, so it's not likely that zonegran would stop my seizures completely. And I don't want to experience more side effects or deal with the process and risk of weaning off another drug. I really need to be at my best to do my job. But I don't want to keep having seizures like this. Does anyone have any thoughts on how I can better weigh the benefits and risks of switching to a new medication, or any other advice? As an aside, does anyone else experience more seizures on weekends?