Murphy's Law: Whatever can go wrong will.
That being said, good luck on hatching at least a couple little roos. That way you can choose the best to keep. Also, with 18 hens, you really need at least 2-3 roos to keep fertility up. You are likely to have MANY unfertile eggs simply because your poor roo was outnumbered. Eggs should be fertile for at least 2-3 weeks, possibly as long as 4 weeks after your roo is gone. You may want to collect a few more just to make sure you get some fertile ones. You can always sell or give away excess chicks.
That being said, good luck on hatching at least a couple little roos. That way you can choose the best to keep. Also, with 18 hens, you really need at least 2-3 roos to keep fertility up. You are likely to have MANY unfertile eggs simply because your poor roo was outnumbered. Eggs should be fertile for at least 2-3 weeks, possibly as long as 4 weeks after your roo is gone. You may want to collect a few more just to make sure you get some fertile ones. You can always sell or give away excess chicks.