Is there something anyone knows of that you can apply to the surface of a board game to protect it against wear so that it lasts longer?
The usual recommendation is to get a sheet of plexiglass (known as Perspex® in the UK) and lay that across the board when you're playing. It's an especially good solution for "board" games that don't actually have a board.
Well-made board-backed games don't really need any help, but many small-press games have the board printed on stiff card or even paper. Paper gaming surfaces go back at least to SPI's foundation in 1969, and so do plexiglass coverings to prevent them getting ruined.
I found this on a BoardGameGeek thread:
You can try this...clear wallpaper, avaliable at any home improvement store and even Walmart, if you're lucky enough to find it there; about $10 a roll and the roll will do the tiles and more. The clear wallpaper will have to be cut after application (it's self adhesive), will have to be trimmed with an craft knife. Hope this helps. I'll be trying this on my set and I've used the clear wallpaper on other games over the years to protect them and 20 years later a lot of them are still in mint condition.
Warning, don't buy the frosted clear wallpaper, you can't see through it.
While I haven't tried it myself, it looks like it might be worth a try. Maybe on a cheaper game first, so that if it doesn't work, you haven't screwed up you're favorite game.
I will go to the local Fred Meyer today and see if they have something like this, and if so, try it out myself.
You might also try clear contact paper.
You could always use the original plastic shrink-wrap that the game shipped in.