Originally Posted by
Tenerife
If you are meaning the "Herbst Spezial" (Fall Special) tickets - the promotion has been extended up to Dec. 2008 - they must be bought no later than 3 days before you are planning to travel.
But AFAIK it's first-come first-served with limited availability... so you may not necessarily be able to get the special fare three days before departure.
For the OP - unless you're in a rush it's probably advisable to buy your ticket for a later train. It's better to hang around sipping coffee for an hour than to miss your train and have to buy a full-fare ticket. 1.5 hours should normally be enough, especially if you're arriving in T1 (you have to allow an extra 15 minutes or so for T2), but it's still a bit of a gamble. The alternative would be to buy a full-fare ticket which is valid on any train.