The rings of the size officially called Mini are deliberately narrow, so that the wallet stays flat and can be opened out and written in comfortably. A complete year's diary together with address and note pages inevitably bursts that limit; the organiser can then only be closed by force. This is no defect in the piece and no fault on the user's part, but a design decision, and one taken in the same way with other ring-binder systems of this size.
The practical answer is either to put in only half a year at a time or to use a space-saving diary with a week to a page, or a month across two pages. Since Montblanc is not a maker of diary systems, its own range of inserts is thin; suitable inserts and accessories in the Mini format are offered by Filofax, with the widest choice, and by Succes. Anyone wanting to carry more on a permanent basis will have to move to a larger ring binder, and with it lose the handiness that is the whole point of this format.