Thank you for writing a review but sorry that you found this to be an issue. You are correct that the reader will run hot when it is working. Transferring data at these speeds will cause the device to get hot and it is alarming to some people that have not experienced that before. When you leave it plugged in and drawing power it can stay warm as well. I have this same issue with an external SSD attached to my computer. Even when it is not working, it gets hot while connected to the USB port. This heat in no way affects the card or the reader and it is fine to leave it plugged in. Please contact us at firstname.lastname@example.org if we can be of help.