A man may play chess with a friend for thirty years without knowing his political opinion, or he may talk politics with him for as long a time without knowing about his personal life. 

【翻译】一个人可能对其政治观点的浑然不知情况下，和一个朋友下棋30年，或者对其个人生活浑然不知的情况下，和他谈论政治一样长的时间。

as long a time 是个“比较”句型的省略说法，等于：

as long a time as thirty years：跟30年一样长的时间（实际上也是指30年）