A while ago I was getting impatient with my slow progress learning Japanese vocabulary and I started wondering how I could speed up my learning. I came up with the idea that I would increase my answer speed from 10 seconds per card to.. closer to 5 seconds per card! The idea behind this was the (wrong) assumption that I would spend half as much time answering the correct cards – leaving more time for extra reviews of incorrectly answered cards. Fortunately, that was such a bad idea that it didn’t take long before I realized that the opposite strategy was actually much better.
Since then, my strategy has been take as much time as necessary to answer correctly. Cards that I cannot answer correctly are studied thoroughly until I am reasonably sure to be able to answer the next time around. This has brought my average to over 12 seconds per card, however I am answering many more cards correctly, therefore, spending a lot less time on multiple incorrect answers. Additionally, I feel that the process of answering correctly is fixing the correct answers in my head with a lot less effort. In the end I am spending noticeably less time studying the same amount of material with better retention.
So I encourage you to try slowing down, to go faster.