when should i stop this heavy weight training, and start my power / speed lifting and technique work?
If by heavy weight lifting your referring to the use of high loads and low reps I don't think you need to really ever stop it. You can reduce the volume and put it on maintenance mode but stopping it altogether probably isn't the best idea. Also I'd make it a gradual transition to a more speed-power emphasis over the course of the year rather than an abrupt change.
what time of year is speed development meant to begin?
Speed can and should be developed in some form almost all year round for multi-athletes.
and how would you guys go about training for the ten events ?
There is no easy answer to this question as it's one of the most difficult training problems in track and field. The best answer I can give is to focus on event commonalities and train for overall speed and power development.
would you use a two week cycle to cover all events?
Not necessarily although I have seen some do this.
and finally any training schedules on here from athletes with 7000+ points?
Not that I'm aware of.