You have 11 months from purchase to activate your pass if it a mobile version. With paper passes you nominate your start date on purchase (again up to 11 months from purchase) but it cannot be changed without buying a new one and then exchanging the old one with a change fee of 15%.

Once activated you have 1 month to travel, so a pass purchased today can be activated until Dec 9th and then one month travel, after date of activation.

Many thanks. P

IF you are sure that you will not start the trip anyway soon-wait till the spring-sale that usually comes along-10 or 15% discount. Even for most promotional passes the same holds: have to start using it 11 months after purchase. There is not any advantage in buying long before now.

Thanks for the tip. P