This one excerpt all at once shows my love-hate relationship with both the genitive and with Charles Ellicott's commentary on the Pastoral Epistles (amazon.com). Here he discusses επαγγελιαν .. ζωης in 1Ti 4.8:

'promise of life.' The genitival relation is not perfectly clear. If it be the gen. of identity or apposition (comp. Scheuerl. Synt. § 12.1, p. 82), ζωη, the import or rather object of the promise, would seem at first sight to involve two applications, quantitative ('long life,' Eph. 4.3, De W.) when in connexion with της νυν, qualitative ('holy, blessed life') when in connexion with της μελλουσης. If again it be the gen. of reference to (Huth., comp. Alf.), or the point of view (Scheuerl. Synt. § 18. 1, p. 129 sq.), ζωη retains its general meaning ('vital existence,' etc.), but επαγγελια becomes indefinite, and moreover is in a connexion with its dependent genitive not supported by any other passage in the NT. This last objection is so grave that it seems preferable to adopt the first form of gen., but in both members to give ζωη its higher and more definitely scriptural sense, and to regarded it as involving the idea, not of mere length, or of mere material blessings (contrast Mark 10.30, μετα διωγμων), but of spiritual happiness (ευδαιμονια, Coray) and holiness; in a word, as expressing 'the highest blessedness of the creature:' see Trench, Synon. § 27, whose philology however, in connecting ζωη with αω, is here doubtful; it is rather connected with Lat. 'vivere' (Sanscr. jîv); see esp. Pott, Etym. Forsch. Vol 1. p. 265, Donalds. Cratyl. § 112, Benfey, Wurzellex. vol. 1. p. 684. There is a good treatise on ζωη in Olsh. Opusc. p. 187 sq. (Ellicott, 61)

First, on genitives. Does anyone seriously treat genitives like this with regularity? Is anyone consumed with classifying genitives (let alone datives, accusatives and nominatives)? Does one really need to label it in order to think about what it does in the passage; to the point of letting the label determine what the genitive can and cannot do in the phrase in question? I don't. And I can't imagine myself attaining command of the nearly 100 types of genitives that Wallace alone isolates and identifies. Why doesn't one simply just look at what the genitive does in a case without feeling a need to put it in a box?

Second, on Ellicott. Can you see why I love him and hate him, all at the same time? The references are great, the discussion makes you think. But it's tough to read. His conclusion is that " ... it seems preferable to adopt the first form of gen." (what's the 'first form' again?) and then gives it his own little twist. That's the frustrating part—why go to the problem of classifying it if your classification is going to be unique? Why not just discuss the function the thing?? On the plus side, you see all sorts of references (to grammars and syntaxes, to commentators, and to other references); this one doesn't even begin to list classical references like many of his other comments do. But it's a pain to wade through.