My solution was to produce an undated monthly calendar page. I printed, punched and filled in a set for the rest of the year and slimmed down my binder quite considerably. Here is an example sheet:
There is a column next to the dates. You can either write in letters for the days (M, T, W...) or you can do what I've done and shade the weekends.
Now I can capture appointments and events several months out without overstuffing the binder. As the month comes nearer, I can transcribe these details onto the main diary sheets for that month and insert them.
You can download this double-sided page in either editable Word format or PDF format. Either way, print double-sided and trim using the printed crop marks.