That's a good rule of thumb when it comes to cilantro. Fresh herbs can cost you an arm and a leg so I generally use some dried herbs when I can. In my opinion, the difference between fresh and dried oregano, for example, is hard to taste.
But there is a huge difference between using fresh or dried cilantro. Guacamole recipes usually include some cilantro. Trust me: the taste of your guacamole will be much blander if you use dried cilantro leaves.
Fresh cilantro is also a great herb to use for marinating tuna or salmon for the grill or broiler.