Have you considered the Anki app? I've been using it for my Greek vocabulary for over a year and I'll never use anything else. I'll get a Greek word and after viewing the answer I'll say that it was easy, medium or difficult and the app decides when I need to review the word based on my response. An example would be the word kai which means and. The first time I said it was easy I had to do it again in a week. The second time it was easy I had to do it again in a month, then 3 months, then 6 months... So there are things I won't have to review for a year, but if I say it was hard I'll begin doing it more often. It's so fabulous. And free.