longtime
with ages
inveterately
at length
since long
longwhiles
since a long time ago
from way back
until the cows come home
until the cows freeze over
imperishable
enduring
abiding
since Skippy was a pup
since Hector was a pup
long-awaited
forever and a day
blue moon
long-standing
eternity
anciently
yore
at last
for England
no end
go back a long way
lang syne
lasting
way back
hot minute
eon
lifetime
donkey's years
donkey's ears
long-lasting
dog's age
durable
long-lived
protracted
light year
crow's age
permanently
macrobiotic
coon's age
longstanding
years
many moons ago
for good
longstandingness
long-lost