Just wondering how many passes you can have at the one time? Is it limited or? Thanks
Depends on what type of vouchers they are.
Where NowTV Gift cards and NowTV Voucher codes it is normally one voucher per a pass where you can usually apply a new code in the last 30 days of an existing pass finishing.
Where with the vouchers that comes bundled with the stick and box if you are on an existing offer over 30 days or more they will be saved in your account.
Also double check the T&C's on the voucher where they will have a different expiry date before they become invalid to use on your account.
Most vouchers come with a 12month time limit, other vouchers from Game i believe they have a 6 month expiry date, where promotional vouchers may have a short time limit to use them.