Partial Flowering???

I plan to germinate soon and was thinking about veggin half of my crop for a month or month and a half and then start flowering them and let my other half veg for about 2 months and then start flowering them. i want to get the first half in the shortest amount of time but still have some growing to fall back on. Would veggin for this amount of time be okay or should i veg longer and also if I do this about how long would it take to flower its is just some seeds i got from a friends stash but it is sativa dom.

well cosidering its sativa dom, it'll be longer, around 9-11 weeks.

so would it be better just to start them on a 12/12 cycle???