In this investment, whatever quantity you invest in S&P today will very likely double by mid-2018. A regression r(0.975) starting at 2009 suggest that the price will continue to rise steadily. Please note that past performance of this instrument is not an indicator of future results however the S&P has always been an outperformer and it is difficult not make some profit in the longer term.
"If you aren’t willing to own a stock for ten years, don’t even think about owning it for ten minutes" - Warren Buffet
The price has gone up as expected for this "relatively safe" long-term trade. The current Return On Investment is 22% so far.