Yeah Singapore_Air, it would be fruitless to try get any prices more than a year in advance because they change every 3 months I think. Bookings are only accepted 1 year in advance, while the actual price is only confirmed about 3 months in advance. For example, I'm going to Christchurch next month and the final price was only confirmed in late September.
Also, lots of things can happen in a span of one year that may change ticket prices. For example, the November-December period's the Singapore school holidays and thus SIA increases its fares to popular holiday destinations by a few hundred dollars. When I went to New York last year, it was S$1600 (US$888, 627 pounds). However, this year, with flights being so empty, it's only S$888 to get to anywhere in Europe or USA. (US$493, 348 pounds) Northwest is only charging S$599 to anywhere in the USA. I wonder if that's below cost.
Hope this helps.