I followed that instruction to the letter and last year lost one because I cut it down too low. This year I only trimmed them down to where the new leaves were forming. Whatever is left from last year is very bushy and full. I will trim mine late in spring from now on.

Agreed -- I don't cut back caryopteris until the beginning of May when new growth is coming out well. I've also found hardiness of the green leaf cultivars to be variable -- one plant makes it and the one next to it is dead. The golden leaf "Worcester Gold" has been exceptionally hardy with lots of bushy new growth. The green leaf cultivars also appear to be short-lived -- my 3 year-old hedge of 30" plants doesn't show any signs of life this spring...so sad!