just use radio.. cheaper means of burning in.. 

Most importantly you don't need to be so strict or overly-disciplined in this burning matter. Burning process is simply keep your earphone producing sound. The longer the burning, the better the sound will become, there maybe no specific duration needed for burning. For volume just use your common sense and avoid too high volume that will damage your earphone, and there is no need to keep same volume all the time.

There is also no need to continuously burn without turn off your player. You can burn anytime at period length you like.

Remember that you are also burning when you are listening.

Since you do not have radio. then your mp3 player will be the cheaper source of burning. But then again, using mp3 player might exhaust its battery life (for certain type of batteries).

Some forumers here are willing to turn on their PC for thousand of hours just for burning. Imagine how much electricity wasted there just for this burning thing. Try to get old radio or any radio or even el cheapo radio at pasar malam. It saves your money alot in long term