Thanks so much for these thoughts! Is NVT more vulnerable to the elements than other kinds of leather? I know that is true for the Mansur Gavriel bags, and it makes me nervous about carrying them if it is raining or snowing (which it does a lot in my climate...) But not sure if that is a characteristic always of vegetable tanned leather or just the MG ones.
The Mulberry NVT isn't as delicate as the MG bags, but I apply the Collonil regularly and I like the process of developing patina. My first Bayswater was an olive NVT and having that made me more fearless about using it in bad weather.
If you live in the US you could look into working with one of the Mulberry outlets (there is one in Cabazon, CA and one in Harriman, NY) to see if they have an older Bayswater. Otherwise there are many preowned sites, but do be careful there are a lot of convincing fakes out there!