Originally Posted by
EDFW
If you prefer saving 10-30 EUR at the risk of having to purchase a new ticket should your flight be delayed: Buy the discounted ticket now.
Purchasing far in advance, the savings can sometimes be quite a bit more substantial than that...e.g. this summer, the same VIE-FRA train was 39 Euro if bought in advance on the extremely discounted plan, but full fare was close to 100 Euro.