Triggering an event based on accumulating symbols over multiple reels in a gaming environment

A gaming system comprising:

• a processor;
• and
• a memory device which stores a plurality of instructions, which when executed by the processor for a play of a game, cause the processor to:
• cause a display, by a display device, of a plurality of symbols at a plurality of symbol display positions associated with a plurality of reels,
• responsive to the plurality of symbols comprising a designated quantity of triggering symbols, trigger a secondary award sequence, and
• responsive to the plurality of symbols not comprising the designated quantity of trigging symbols:
• accumulate any triggering symbols of the plurality of symbols that are displayed at any of the symbol display positions, wherein each accumulated triggering symbol is associated with a duration until that accumulated triggering symbol expires, a first triggering symbol displayed at a symbol display position associated with a first reel of the plurality of reels is accumulated in association with that first reel of the plurality of reels, and the first triggering symbol displayed at a symbol display position associated with a second reel of the plurality of reels is accumulated in association with that second reel of the plurality of reels, and
• responsive to the designated quantity of triggering symbols being simultaneously accumulated, trigger the secondary award sequence, wherein the designated quantity of simultaneously accumulated triggering symbols comprises an unexpired triggering symbol accumulated for a prior play of the game and a triggering symbol accumulated for the play of the game.

A method of operating a gaming system, the method comprising:

• for a first play of a game:
• displaying, by a display device, a first plurality of symbols at a plurality of symbol display positions associated with a plurality of reels,
• responsive to the first plurality of symbols comprising a designated quantity of triggering symbols, triggering, by a processor, a secondary award sequence, and
• responsive to the first plurality of symbols not comprising the designated quantity of trigging symbols, accumulating, by the processor, any triggering symbols of the first plurality of symbols that are displayed at any of the symbol display positions, wherein each accumulated triggering symbol is associated with a duration until that accumulated triggering symbol expires, and
• for a second, subsequent play of the game:
• displaying, by the display device, a second plurality of symbols at the plurality of symbol display positions associated with the plurality of reels,
• responsive to the second plurality of symbols not comprising the designated quantity of trigging symbols, accumulating, by the processor, any triggering symbols of the second plurality of symbols that are displayed at any of the symbol display positions, wherein each accumulated triggering symbol is associated with a duration until that accumulated triggering symbol expires, and a first triggering symbol displayed at a symbol display position associated with a first reel of the plurality of reels is accumulated until expiration in association with that first reel of the plurality of reels, and
• responsive to the designated quantity of triggering symbols being simultaneously accumulated, triggering, by the processor, the secondary award sequence, wherein the designated quantity of simultaneously accumulated triggering symbols comprises an unexpired triggering symbol accumulated for the first play of the game and a triggering symbol accumulated for the second play of the game.