The is a product specific for filling cracks, it advertises 25% expansion capability (sorry I forgot the name but will try to find it). In any case I was able to clean out a 12 foot ceiling crack in a garage, fill with this material and let dry. Since this shrinks into the crack a second coat maybe required, but it remains flexible (spackle does not) and it appears to stop the crack. This would be my first choice of repair. This main thing is to make sure the crack is cleaned out of any dust or loose debris.
Hope this helps.
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Pennsylvania, for 60+ years, most recently, Allentown, now TV. 
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