Does anyone know how often Garden Joy offers videos to watch for Diamonds?

Does anyone know how often Garden Joy offers videos to watch for Diamonds? I seemed to be doing okay on time with Garden Joy because I got coins for voting every day and at least some extra Diamonds for watching videos. But, today, I just kept getting the message that no videos are available. I have tried the Tap Joy surveys and every once in a while I get some Diamonds awarded. Like most surveys these days, there are a lot more disqualifications. I am at level 12. I am about to cut my losses and move on to another game.