There is no data. Every variety of pot is different, and even if someone did compile the data for what they were growing it would be like comparing apples and oranges for someone else's grow.
You seem to have some misconceptions about flowering times. This is genetically set... and you really don't have a choice to go longer, such as to go for volume... the plants are done when they are done and going much longer than that either sends them into a second blooming effort in order to produce seeds, or they simply die.
Most people harvest their plants when amber first starts appearing on their upper buds and like myself, they shoot for 2% amber before harvesting. Going longer, and producing pot that has gone even 10% amber produces a very strong body high product that is too much for a lot of people... we call it couchlock, and for many people it is to be avoided.
So the vast majority of people harvest their pot before it even gets to 5% amber. The thc content in the trichomes is actually highest right before this point, when they are all milky, but very few people like that strong heady high that results. When the trichomes have ripened to amber they are just starting to lose one type of potency while gaining another, and you don't really start losing overall potency until later on, when the trichomes start going from amber to deep red or black. It is at this point the THC is starting to break down, but NOONE harvests at this point if they know what they are doing.
Anyway, harvest is not where you decide to go for volume... that happens way back in veg when you have a choice in photo period plants to either switch them to bloom mode or not. It is said that every week you keep the plants in veg past maturity, you double the final yield. This is going for volume, when instead of vegging for a month and quickly going to bloom with a small plant, you veg for another month or even longer and create a monster bush that can be sent to flower... now you are talking volume... but again, it will only bloom for however long the genetics of that variety tell it to.
So on your plants, you should have gotten a flowering time from your breeder. No matter how long you have been in veg, your flowers look like they have been in the flowering mode for a week at best. If this is an 8 week flowering plant, you still have 7 weeks to go.