ALZ stages: How did you know when your LO move from Stage 4 to Stage 5?

My LO was just diagnosed with ALZ. I've taken the Dementia Behavioral Test (DBAT) a few times to assess which stage my LO is in. Right now, my LO is ticking off nearly all boxes in Stage 4. The LO is still living (mostly) independently at home -- although my family is working to establish a home care companion and we are starting to be concerned about the LO's driving ability/confidence. I'm just curious for others who have followed and understood the various stages of this disease: how did you determine your LO moved from Stage 4 to Stage 5? Was it quick or gradual? At what stage / point (and how quickly) did your LO move from care companions to long-term care?