Tape has metallic particles in it and when its in the air (which contains moisture) the magnatism from the heads create a corrosive environment. Corrosion is bad for heads. On the tape side the heads will still be activated somewhat and that will cause a slight particle shift or random scatter. Its very slight but its works against you because its a form of noise.
reel buzzer - SoMm is right on all counts. The biggest danger to leaving tape on the machine is that when you power the machine on, the in rush current through the heads can induce a magnetic field and erase portions of your tape... I often leave tape on the machine overnight but I do take care and pull the tape away from the heads before powering the deck on or off.
The biggest danger to leaving tape on the machine is that when you power the machine on, the in rush current through the heads can induce a magnetic field and erase portions of your tape...
And some transports have been known to engage and snap the tape or dump edit onto the floor. They don't say Ghost in the Machine for nuthin And don't pull a slipperman either