Hi pull-up
1103 days is definitely not the norm, while I am not aware of Zeddy's specific situation, he may have had medical or educational problems to overcome before being put into the flight screening pool. Generally those who have good grades, perform well at the YOU session and assessment day and are deemed a competitive candidate will be given priority for a slot at flight screening.
As for extra curricular activities, my suggestion is to take on as much as you can without sacrificing your grades. Having a busy schedule is a good look as life in the military can be quite hectic. I would suggest air cadets, a team sport and a community service of some description. Hobbies are a good way to show your enthusiasm, for instance, remote control models, plastic modelling (VERY handy for the selection process
) or even reading magazines.
And don't worry about your age, I personally know a couple of blokes who have been selected recently for DEO who are 17 years of age.
Hope this helps and good luck...