I have to say never. I have to admit that I don't listen to music as often as others. When ever I do listen to music though I'm either out walking or running, I never sit in the house and listen to music. As result I'm never in the position to charge and listen to music at the same time, this is also helped by the fact that I generally only charge my iPhone at night time when I'm asleep.
All in all the removal of the headphone jack won't affect me as my headphones that I have can just use the adaptor thats supplied.
I honestly see this as Apple doing the pushing before manufacturers of headphones push phone manufacturers to no longer need a headphone jack. Wireless headphones are becoming more and more popular, either a manufactures turned around and said 'You know what, we can do without the headphone jack', or consumers would say 'Why do we need the headphone jack with the popularity of wireless headphones and how cheap they can be made now?'