sorry for the question but I haven't made any transaction since now; how long is there to wait for a transaction before BTCs change owner? I heard that the velocity of transaction is proportional to the number of users of the net. Am I wrong?

@ Haxxy: Why do you say that "The last thing bitcoins need is a physical transfer medium"? Don't you think that a device able to be brought with you can be very useful and helps increasing the spreading speed of the currency?