Just think of it this way. In your fermenter or in secondarys there isnt really pressure on them and they are fine. You will be fine off pressure for quite a while. The only thing that may even remotely cause a problem would be if there are wild temperature swings on the keg that would cause expansion/contraction and suck anything nasty in through the leak. Kinda of a low chance of that happening though. When you do get your tank refilled, find that leak. Nothing worse than an empty CO2 tank when you want a beer.