E-PM1 bulb feature - any way to avoid holding button down?

I recently purchased an E-PM1 and yesterday I was trying to take a photo with a long shutter speed (I was trying to capture the milky way!).

My question is about the bulb feature, which is the only way to take photos with longer shutter speeds than 60 seconds: do you really have to press and hold the shutter release button in during the entire exposure? It seems a bit strange to me!

I would like to put the camera on a tripod, and then press the shutter to start the exposure, but then I would like to just wait until it's time to end the shutter and press the button again. I couldn't find an option to do this -- does anyone know if it's possible?

How do people otherwise use the bulb feature? Do you really sit there and forcefully hold the button down, adding shake and tension on the camera while carefully composing your shot on a tripod? How did Olympus think here?!

Cheers,
--
David Tenser
My camera equipment: http://djst.org/camera/