Quote from DeltaSpread:
You mainly use them for the following two scenarios.
When you think a stock has real promise, technically or fundamentally speaking, for the next month or more with a nice move to the upside or downside, SSF's are great because they wont tie up capital or require you to use margin.
REAL world example: A great time to load up on SSF's would have been this past July. Take Apple for example, sitting in the $50 range for over a month. It now trades at $90. Take your pick. There are a boat load of stocks that had these kinds of moves, like RIMM, ICE, GOOG, etc. SSF's would have been huge for any of these equities.
Also if you anticipate something dramatical or sudden happening like an earnings announcement, etc. that will really move the stock, SSF's will work.
Bottom line is, you need legitimate moves in the underlying for you to make any money on SSF's. Forget about scalping and general shorter term trading. The spreads are not ideal and if you have any kind of volume to unload, the liquidity is another potential issue. What will outweigh these logistics and really allow you to maximize the value, is a nice $2, $3, or more move in the underlying stock.