long-time       
adjective [ before noun ] uk/ˈlɒŋ.taɪm/ us/ˈlɑːŋ.taɪm/
C1 长久的,长期的
used to say that someone has been in a particular position for a long period
  A long-time friend of the chairman said she had expected the resignation. 董事长的一位老友说她曾预料到会发生此次辞职事件。 
 - More examples
 - He is a long-time supporter of the Labour party.
 - She is a long-time friend of the family.
 - Green, long-time editor of the journal, today announced his resignation.
 - She as his long-time business partner.
 - They are long-time supporters of the arts.