You can 10draw any time and it'll add up :D
Once you hit around 60draws total...you are due for a "rare" such as Pain, Sage Naruto and so on.
Which rare you get is random. That's the only thing random about treasures lol

I did 5x10draws and a single 10draw(later that week) and got Ao. So you can either save up or use them every 10~