@13 most probably to do with rest requirements however sometimes BA want us to be an extra day downroute (for instance India) to serve as a back up crew in the region.
Doesn't happen often anymore though. Summer/Winter schedule change over sees a lot of positioning. It's pretty rare these days to position anywhere on the network in my experience.
@Ozzie, I certainly wasn't advocating an axe but some don't even seem to want to engage in constructive dialogue. That blinkered view is a symptom of BASSA's bunker mentality over the years and now comes to a massive crunch because of the unwillingness to change.