The tiles are pretty tight together, most liquids will not go between the tiles (yes, if you leave it for days some will seep down). I never worried about spills, cleaned them up when I had the chance and when I pulled up the floor 9 years later to move I was pretty surprised at how clean the concrete was. The only area that had any stains was from under my lift which saw heavy use and even there it was not bad, cleaned up easily for the next owners. In my new house I placed the tiles on the slab and I expect to never see that slab again in this lifetime.
The only thing I did differently in my new house was leave a corner 7'x8' without Racedeck as I was tired of melting tiles when welding so now I have a corner for my metal grinding and welding. In my old garage I would lay a fireproof blanket down, its nice not to have to do that if you have the space for a bare concrete area (I do).
Mike