Definition of "long-standing"

long-standing

adjective
comparative longer-standing or more long-standing, superlative longest-standing or most long-standing
1. Having existed for a long time.
  Quotations
  Forty-five years ago, Crewe was witnessing the first year of the revised timetable associated with the 'Electric Scots' services, following inauguration of through London-Glasgow electric running in May 1974. Except for Euston-North Wales traffic, the long-standing practice of motive power changing at Crewe had ended.
  2020 June 17, David Clough, “Then and now: trains through Crewe”, in Rail, page 60
2. Having been done for long enough time to become convention.