Shared printing problem

I have an imac and a macbook pro both running Tiger and in a network. My imac has the connection to the printer so I use printer sharing for my macbook pro. I have noticed that whenever the imac is sleeping or turned off-My shared printer disappears off of my macbook pro and it won't detect it at all. When I simply wake the iMac from sleep or turn it on it works like normal again and the shared printer on my laptop will reappear soon. Is this how printer sharing is supposed to work? I thought that it would work whether the host computer is on or off? Although it does make sense that since the host is offline it takes the printer too, hmmm.