I very much doubt steam would just blanket refund you for any preorder regardless of the situation. If you've bought a significant amount of games with it then maybe not. If theres been quite a long time between buying and refunding again probably not. If you've blatantly clocked up a lot of hours on all the game you bought with it, again, no.
They'll have guidelines surely, because otherwise its a very abusable system. Consider that you can buy something, download it, set the computer to offline mode, refund it and never have to worry about it. Dunno if theres any way to detect it (such as if you came back online and it was detected) but it sounds like an instant permaban if caught.