I use the same parallel port for printing on a printer and networking with my laptop without big problems. It takes less than one second to switch from printing to networking. I just add a cheap manual switch between the parallel port, the printer and the laptop. The cable between the switch and the desktop computer is a fully connected one. The switch is just the one used to shared printers when no network is available. It works.
Sometimes, the kernel is not very happy because it can't finish its network job. In that case, I shut down the plip interface and restart it when needed.
I bought a new parallel card last year but it is still in its box. I'll write an "install a second parallel port" when I succeed in opening the box and add that beautiful card in the last connector I have left.