Wormholes

I've always wondered: When closing a static, how is the next static's destination chosen? I can think of several possibilities:

1. Totally random (as far as coded randomness goes) , i.e. it could lead to any eligible system including the one where the last static went
2. Random, but not to the one that just got collapsed
3. Systems that were recently connected (since last downtime?) are excluded

Other restrictions could apply. Maybe systems that already have a lot of wormholes are not eligible, or even preferred to create hubs?

I hear some corps with a static C6 sometimes roll their static many times in a row to get the same C6 again, for invasions. Maybe they can shed some light on this? I guess if the next system is always randomly pulled from the whole pool of C6's, it would usually take *very* long to get the same C6 again, even though there are not so many of them?