I was diagnosed with Narcolepsy in August of 2012. I was prescribed 25mg of extended-release Dexedrine (dextroamphetamine) in the morning, and I found it was awesome in the morning to get me going, but at lunchtime I was so hyper and twitchy I couldn't focus on anything and I felt like my heart was always racing. I lowered my dose to 15mg in the morning, and found that was better for sure, enough to keep me falling asleep after lunch, but not so much that I was twitchy or anxious. However, with the lower dose it did not last as long, and therefore I found myself extremely tired in the early evening 7-9pm usually. I'm talking hardcore sleep attacks. I would be getting home from work at 7 or 7:30pm and wouldn't even make it to the house I would just fall asleep in my car immediately after turning off my engine. Scary. My doc prescribed me a 5mg short-acting version of my same Dexedrine. It worked great to get me over that crash, but didn't keep me up as long as I took it at least 6 hours before I wanted to go to sleep. I still have trouble winding down after the day, and that is most likely due to my delayed sleep phase disorder, however it definitely helped me because I was more tired (crashing) after the 6ish hours and it was easier to sleep since I didn't have an unwanted nap earlier in the evening. I still, occasionally, end up napping at random times, in undesired places, however it is much more manageable and I have learned not to sit still for too long, especially at certain times.
One thing I will mention about my experience with this medication, is that it is really easy, because you are using the meds to stay awake, to start thinking that you don't need as much sleep. Before medication, I would sleep on average 9-10 hours during the week or working days and more like 12 on weekends or non-work days. Since being on medication, I have been sleeping more like 7-8 hours on week days and usually not more than 9 on weekends. I'm not saying I sleep too little now, or that my body needs more, simply that it is sometimes hard for me to justify sleeping for more than 6 or 7 hours when I know that I will be just as tired in the morning after 10 hours of sleep. My mind starts playing tricks on me. Well if i'm going to be tired tomorrow anyway, why not stay up another hour or two and get some more things accomplished. It's hard to know how much sleep your body actually needs when it always tells you you need more That being said, I have started to notice the difference between sleep attacks, and my body being exhausted. It is a different kind of tired. It is almost like one is mental, and one is physical. So ya, it has been quite the learning process.
Also, I take periodic breaks from my medication if I have a day off and plan to just hang out at home all day, or just having a lazy day I won't take any meds and usually end up napping and not being very productive, but I find that it makes the next day that much better because I feel so great having energy at least! It is weird to feel that sluggish, un-motivated, walking-under-water feeling after feeling so good and full of energy while on medication. Helps put things into perspective for me, and makes me grateful for my little pills, while also helping my body resist building up a resistance. lol.
So clearly that was not advice, simply experience. My advice is play with it. I haven't experimented a whole lot lately simply because I feel that my current arrangement works for me at the moment, but It was not my first and I'm sure it won't be my last. Try more or different kinds or whatever your options are, because you may not realize how much better you can feel until you feel it. (that comment was lame and I apologize, but you know what I mean)
Best of luck with your journey!