One of the major problems with downtime is that your trades will continue sending into a black hole, especially if they have a set force. Your end is down so it's not counting the hits, and you end up with an unbalanced trade. After you pop back up their end sends back less because the return from their perspective is now 150% instead of 120%.
For your big trades it's often easier to both reset your stats and then do a force to grow it from scratch again. That's assuming you can get into contact with them. 
You could also set up a second site on a different host. If one has downtime, use the remaining site as a feeder once it's back up again.
I think Choker is the only major traffic guy that lets you start traffic orders by yourself so it's probably worth having some funds sitting in your CTTS bank for emergencies.