It's always best to use as many as you can at all times when growing with CFLS.
However, to answer your question, it would be wise to use more light during flowering as this is when plants really need all they can get. You can get by with using just the same amount as you used for veg. I wouldn't recommend lowering the light strength during flowering as it will only lower your final yield.
I need help this is my first grow I got a hps light and my grow mico grow big and bloom and free seeds but I don't know how to get seeds like white widow and trainwreack so can any one help me email me and let me know how I know you have to get an international pre paid gift card but where do we get them