Ive grown big bud from nirvana along with their northern lights and their nlxbig bud.And just to say i dont think 20/4 light cycle would hurt its just it was a new thing cuz most growers stay at the same light cycle threw the whole veg stage and only switch lights during flower.But any ways there isnt really a point when its ready to flower...i meen theren is wich is when it shows signs of preflower but there isnt really a specific time you HAVE to start flowering...you can flower at 4-7 nodes by force flowering and your plant will react just as good as waiting for the preflowers.But on the other hand from all my grows ive noticed that the longer the plant is in the veg stage...the more yield you get.Big bud is a high yielder anyways under the right conditions so im sure your yield will be good.Also you have to take into account how much space you have to grow...cuz it will grow some more when you put it into flowering so dont keep it in veg to long if you have limited space.And another piece of advise...it doesnt really matter what strain your growing most growers will all still tell you the standard veg time is 2 months and im sure most would say to start flowering now.....yes some strains take longer in th veg stage then others but big bud isnt one of them...its an easy to grow strain that is quick.