i don't think the "deep" is anything you can quantify. in fact, i think both the idea of the landlord, and the deep, are metaphorical. IE, the landlord won't really be painting over anything, but someone is going to occupy this apartment after this couple, and all of it will be erased. the relationship will be painted over. in the same way, the "deep", i think, is merely the speaker's desire for someone, someday (possibly the lover) to remember the whole thing.
i don't think the "deep" is anything you can quantify. in fact, i think both the idea of the landlord, and the deep, are metaphorical. IE, the landlord won't really be painting over anything, but someone is going to occupy this apartment after this couple, and all of it will be erased. the relationship will be painted over. in the same way, the "deep", i think, is merely the speaker's desire for someone, someday (possibly the lover) to remember the whole thing.