What happens to the Mode Points if i don't redeem them, is there a validity period or expiration date for the Mode Points?

Your Mode Points will be kept safe in your account. There is no time limit in which you must redeem the points.
It's recommended to create a goal for the Gift Card and/or Physical gift item you want to obtain, and if you've accumulated enough points, we suggest redeeming the Mode points and setting another goal for Gift Card or Physical Item.