long-standing
adjective
[ ˌlɒŋˈstandɪŋ ]
• having existed or continued for a long time.
• "a long-standing tradition"
Similar:
well established,
long-established,
established,
fixed,
time-honoured,
time-hallowed,
abiding,
enduring,
long-lived,
surviving,
persistent,
prevailing,
durable,
perennial,
firm,
constant,
deep-rooted,
steady,
stable,
staunch,
long-term,
