Don't ever buy FAZ,FAS, FXP, SKF of any of these so called 2X, 3X, and even 4X leveraged ETFs. If you're savvy enough then buy it for a day trade or if you are sure about the direction maybe hold for 2-3 days. Just compare the performance of these with actual index they try t0 mimic... it is terrible. The only people making money are the issuers.
Also worth noting that the fund prospectus clearly states that nothing is guaranteed.
There is a class action lawsuit against Direxion whereby one of their bear funds did not match 300% of the inverse performance of the index it tracks. But with the disclaimer that nothing is guaranteed I cannot see how anyone can win in court.