I usually play with two continent maps. Often I rely on the civs on other continents to be trading partners. Usually, if one of my neighbors is starting one war with me, that neighbor is going to start another some time later, and on that assumption I will start the perpetual trade embargos.
It does come with risks- if a new age unfolds, and I don't have a strategic resource under my control, and my allies don't have spare to trade, and I'm not in a position to take it from a neighbor. In that case, I can choose not to renew the trade embargo. The trading reputation is tracked separately from attitude, so as long as I haven't been breaking trade deals, I can trade without paying a premium even if my enemy is furious with me for all the embargos.