You can purchase a very cheap item from the store that will combine your items' durations - for example, you can purchase the Active Adder to combine all of your Rush II's into one, creating a 120 game Rush II from six 20 game Rush II's. This is currently possible for Active II skills, Passive II skills and Packs(HP, RB etc), all up to a cap of 200.

ActiveAdder BOT type: Any Item type: Coupon Req. Level: 0

Can be purchased for 500 Gigas

Combines active skills into one item, up to a max of 200 games on an item.

PassiveAdder BOT type: Any Item type: Coupon Req. Level: 0

Can be purchased for 500 Gigas

Combines passive skills into one item, up to a max of 200 games on an item.

PackAdder BOT type: Any Item type: Coupon Req. Level: 0

Can be purchased for 500 Gigas

Combines canister packs into one item, up to a max of 200 uses on an item.