How long the whipped cream lasts in a cream dispenser depends on the expiry date of the cream and the temperature that the cream canister is stored at.
You can leave the cream dispenser canister at room temperature for several hours. If refrigerated the whipped cream in a cream whipper will last up to 14 days.
If stored in the freezer the cream in a cream whipper dispenser will last up to 3 months however, frozen then thawed cream can sometimes not be as fluffy as fresh whipped cream.
NOTE: after storing your whipped cream in a whipper in the fridge or freezer be sure to let to come back to room temperature before releasing the cream from the dispenser. This is because cream at low temperature becomes more like a solid and may stick to the bottom of the dispenser and not dispense properly when at low temperatures.