Here’s a data point: am using EF 1.2 with a 1.2 Gb library collection, of which roughly half are 80K+ emails, and most of the rest are several hundred PDF’s and web archives. I can confirm that EF works impressively well on a modern high-end MacBook Pro. RAM use is in the dozens of MB’s and CPU use is 0% when idling - IOW, perfect. I can definitely see myself using this for many years to come, scaling up easily as more contents get added (and Moore’s law will do the rest).
Kudo’s and many thanks to M.T. for getting everything “just right”.