what if no case, all overclocked with fans and water coolants?
Its fine unless you have cats
doesn't really matter as long as you have fans on all your rads and you have no kinks in your hose. And Tacopat makes a good point, try to avoid doing this if you have pets, as chewed hoses and large amounts of fur do computer components no good.
The company that I purchase my case was retarted and forgot to ship the front audio cord with it. I had to take everything out of my case and leave it on my desk. (I had even done some pretty epic cable management too!) I thought I was going to have to return the case. Only for three weeks later, just before Newegg's return policy expired, did I receive the audio cable. (Infact I got two, one of them being shitty. The cable came with a PCB and all of the components had leaked/exploded on it. I'm never using that company again.)
But, you should be fine. Just be careful of animals and dust.
Use a test bench, dust could be San issue as well was cats and people