the number after the "reset=" would make the sequence reset to the beginning, if this butten has not been pressed for the said number of seconds. so to get this effect i'd add some more of a non-cd-spell to the end. alternatively you could try out reset=combat (resets at the start of combat - or nocombat for the end of the fight) or reset=target (resets at the aquisition of a new target or nocombat for loosing the target)
and yes, they can be combined (e.g. reset=target, nocombat, 290)
edit: for binding elements i'd use a focus-target, so even if the spell is cast before the old one wears off, the spell will refresh the cc.
#showtooltip [@focus, exists][@player-target, exists]bind elements
/cast [@focus, exists, nodead, harm][@player-target, exists, nodead, harm]bind elements
/stopmacro [@focus, exists, nodead, harm]