How many times a day should I do BTC Stretches

I am a newbie but had been doing manual stretches for a few months before joining this group. Anyway, I have been trying out BTC stretches and although in the video section it suggests up to 5 minutes at a time but how often should this exercise be done per day? I have been doing 3 or 4, five minute BTC stretches a day but can I safely do more? I am after a flaccid lengthening as well as erect so am doing other stretches and jelqs as well.

Any ideas guys?

BPEL 17,0 cm and erect girth 12,0 cm. None pulled flaccid length 11,5 cm as at 29th October 2010

BPEL 17,5 cm and erect girth 12,0 cm. None pulled flaccid length 12,7 cm as at 3rd December 2010

Goal BPEL 18,5 cm and none pulled flaccid length 16,5 cm