Yardenman, know what you mean about conflicting advice (often it reflects gardening in different locations), but sometimes the perennials themselves have to take some of the blame for failure.
An old gardener's adage: if you want to know where to plant a plant, buy three, plant them in three different locations and the plant will tell you where you should have planted it.
Suspect that this refers, at least in part, to micro-environments within gardens.
Still, short of dry, full shade, I do find many perennials still do OK in rather different growing conditions.
Almost all our own Brunnera get soil with a good organic content, protection from the sun in summer and weekly watering in the absence of a fair bit of rain.
Otherwise I'd say the Brunnera cultivars we have are not very demanding plants to grow and do well.
And we've had 'Jack Frost' longer than any other Brunnera cultivar.
I've not had problems overwintering (outside, in a protected place) divisions of many potted perennials, including Brunnera.
I suspect planting directly, after division, in the garden is best.
I (re)plant any time but in summer it's especially important to keep an eye on the watering of the plant(s) involved..
Suspect the best time for me to divide and replant is early in our long fall with it's rain.
At the same time, we've left an (established) Brunnera 'Langtrees' (parent of 'Jack Frost') in a bed we never water, between our's and the neighbouring house, for years.
