DaasYochid,
1. The correct analogy iss buying sifri kodesh from a publisher whose sefarim have been found to have blank pages (which happens all to often).
2. The analogy to a nazir is that a person does not have to add fences unless he has a specific problem or alternatively has reached the level of chassidut as defined by Messialt Yesharim.See also Taanit 11a,Yerushalmi Kiddushin 4:12 and Nedarim 9:1.