Here’s a handy tip from the forum for those etching PBC’s at home: forum post

…about 4 years ago, I saw that someone said that you could protect an etched copper clad PCB with polyurethane once you were done soldering. So as a test, I grabbed a scrap of PCB and scrubbed it up till the copper was shinny. I then sprayed 1/2 the board with polyurethane, and left the other half bare. I put it on a shelf, and it’s stayed there ever since. That was four years ago.