The 100 Mile rule sounds... Interesting. While we have no such rule, my love interests (that is, other than my husband) are all far away, but that's mostly due to meeting them online, so it's more of a coincidence kind of thing.
And I'm not actually in a relationship with them due to the distance, so... Even if I did make a trip, it would be especially to meet them, and my husband would be likely to come along. Sounds far from my situation.
Still, I'm wondering if there are polyamourous people who travel regularly, for their work for instance, and basically have a partner in each place, you know, kind of leading a double (triple, etc) life, except everybody knows.