You have to activate the pass within 11 months from the day you buy the pass. Once you have activated the pass you can travel for 22 days.

So  there is not any reason to buy now if you only plan to go much later.  Prices are fixed till 31/12. Refunds are very, very hard to get and take many monthes. There may -sometimes-mostly only off-season, be extra sales when you can get 10 or 15% discount.

Please don't tell fairy tales. Refunds done by yourself in your account are almost instantly.

That's the main reason not to buy now. There's usually such a promotion in November/December.