They sure look beautiful in the pictures I saw, lived near Santa Rosa
for a couple of years, and don't recall having seen one. I think it is
not a true lilac as I know them even though the blooms look similar,
those are so much more splendid than any lilac I know, including Beauty
of Moscow which I covet but have no room for, did a little googling and
hard to find zone info, but concluded the pretty ones do not grow in my
zone or anywhere near, the west and south. There is a plant in the
family that does, but it is not at all like those.

They are indeed beautiful.
Concha is one of the older cultivers, grows to about 7-9 feet
sometimes
taller. Concha is hardy to about 15 degrees.
For information Ceanothus, locate a copy of Sunset Western
Garden Book. Your library should have a copy. Sunset lists
32 species/cultivars of Ceanothus that are planted in gardens.
Some are low and spreading, some are tall and upright, some are
vase shaped. Average age ( as David R notes) is 5-10 years.
Ceanothus is in the Buckthorn Family.Rhamnaceae
All need excellent drainage. Coastal types can stand a little more
water

Emilie
NorCal