There is also a lot of speculation with mining, because in reality what you mine today can be worth much more in the future. 2 or 3 years to ROI at current price yeah, but you could also ROI in 6 months ! It depends on four factors : the price you paid per TB, network difficulty, block reward and Burst price.
Conclusion : do you believe in Burst ? If yes, invest, if no, don't and regret later :p