As a person who has recently taken the SAT for the second time, I highly suggest taking it twice, the reason is not just so you are used to the test, buy you actually just get smarter with age. I will use myself as an example, I took the SAT in 11th grade and spent several hours studying, and that got me a 1290. A year later, I took in yet again with barely any prep and acquired a 1390, it is important to take it the second time in you senior year, to achieve the highest possible score you can.