This depends on your tolerance for risk. I've seen BR suddenly open SAUA at T-4 Days and have other itineraries where nothing will open up even from T-4 months.

You'll want to assess if anything is interesting with regards to travel during your target date. Major Taiwan event (like a major election) or summer travel means very slim availability.
Off-season travel in the Spring or Fall? Probably a better chance.

I'd expect you will probably need to do a combination of points and cash as I don't see many flights with 2+ more Z availability. Your mileage may vary, however!