The best (least speculative) times to buy SRPT were in July 2012 (when it opened 100% to 7.3) and last week (when GSK's drug failed). Anytime before 7/12 was speculative.
I am in it since 3 years (bought for stupid technical reasons). But, doubled on that eventful day in July 2012, and have been steadily buying since then (24, 30, 40). Incidentally, my wedding was on THE day in 10/2012 (talk about an auspicious event!). I was all set to buy more at 48 10/3 morning, but didn't pull the trigger.
I think the last two weeks have once again changed the perception of the company. Wall Street doesn't like hindrances -- and I believe they are mostly gone now. I really believe this will get very close to $100 in 6-9 months.