I've been on 40mg of Viibryd for about 3 years and worry that either the drug has lost some of its effectiveness or I'm experiencing side effects.

Specifically, I find that while not necessarily depressed my energy levels are decreased and I find too that I pretty much need 9-10 hours of sleep.

When I first started taking Viibryd 3 years ago the only officially approved dose was 40mg. I had been taking 150 mg or brand Zoloft and still went into a depressive relapse. My Doctor had me titrate down from 150mg Zoloft to 100mg for 1 week, 50mg Zoloft the next week and 0 mg Zoloft for the 3rd week. Then he gave me a bunch of starter packs of Viibryd. I titrated up at 10 mg the first week to 20mg the second week. By the end of the second week I could already feels the effects of the Viibryd and the results were positive. This was the first time that I ever actually felt that my anti-depressant was working. I went ahead and went up to 30mg the 3rd week and after that I felt so good that I stayed there for about 5 weeks until I ran out of the starter packs. When I saw my Doctor to get a prescription he urged me to go to 40mg so I did. But it always bothered me a little bit that I was taking more than what in my gut I felt I needed. Anyway the first year at 40 mg was fine and even the second year was okay. But this last year I've felt sluggish (though not in a depressive sort of way). I know it is probably an insurance nightmare to ask my Doctor to prescribe 30 mg as it would involve prescribing both 20 mg and 10 mg tablets. But I believe that now that Viibryd has been approved as therapeutic at 20 mg up to 40 mg a 30 mg prescription is possible.
Meanwhile, I have been able to get clean and accurately splits of the 40 mg pill into quarters of 10mg each using a pill splitter.

So my question pertains to the experience of others in going from 40 mg to 30 mg. And if not that, then from 40 mg to 20 mg and what that has been like for them.

Thanks in advance.