Yet if this is all that a minister reads he will be neglecting his own need to maintain theological sharpness, and his ability to defend truth against error. First hand aquaintance here, alongside some helpful secondary literature, has several benefits. It will mean taking false teaching seriously on its own terms. This forces you to grapple directly with the issues and arguments. It helps to prevent laziness and a dulling of the critical faculties. On the positive side this can only be good for that ongoing discipline of spiritual discernment. There is a degree of credibility in doing this that a reliance on secondary literature cannot supply.
Of course there is an important caveat here. As Phil Johnson once commented, some people only seem to a hold to a view for about eighteen months before they change there mind and embrace something else. In order to responsibly critique an opposing position you need to have a worked out theological framework to begin with. That takes time, reflection, reading (of doctrine, exegesis and history), discussion, debate, prayer, meditation, and suffering. From this, a position of real strength can emerge. And from this framework false teaching can be read, probed, and responsibly critiqued.
To quote from Michael Corleone, that unlikely source of theological wisdom, "keep your friends close, but keep your enemies closer."