I 've pulled down and opened up more of the branches to light, how long should I continue to stake the branches down ?
It's up to you, but the longer you veg the more you'll yield. I like to fill in my screen as much as possible, or in your case I'd like to fill up the canopy area as much as possible, which looks like you've pretty much done. I try to fill in my screen about 75% before switching to flower mode. There is no one right way to do it. It's just what works for you. Eventually there will be no more room for any new shoots. Remember that once you switch to flowering, a plant can double or triple in size.

Is there a point when it becomes counter productive ?
Yes, it would be counterproductive if you already have a thick even mat of canopy, and there would be no place for any new nodes, or shoots. It would also be counterproductive after a few weeks into budding. Once she starts budding up good, you should stop bending or tying down branches.

I think Ive gone from about 15-20 bud sites exposed to direct light to over 100, will all these buds still develop ?
That's the idea, expose more of the plant to the light and you'll get more bud sites. Id say 100 is probably enough. You can make as many as you want, but the more there are the smaller they'll end up. All bud sites exposed to light will develop, but the ones lower down on a stem develop slower and end up smaller than the ones at the top.