yeah deffo keep it going longer man, you can tell when its ready cos the overall colour of the plant changes, as someone mentioned leaves will start to yellow and drop off and basically the bud will just take on a more browny appearance overall if you step back and look at it, not like brown brown obviously, but I guess kinda a slight 'rusty' colour, then you know she's ripe to go! have a look through some grow journals and you can see what I mean for yourself.
Generally the time scale the breeder recommends is like the absolute fastest if you have everything dialed in perfect so if they say 8-10 weeks I normally assume its gonna be more like 10