adj.(已持续)长时间的；为时甚久的
In view of our longstanding business relation, we can consider accepting your counter-offer. 鉴于我们之间长期的业务关系，我们可以考虑接受你方还盘。
On our part, we appreciate the longstanding cooperation between us. 从我们这方面说，我们也赞赏我们之间的长期合作。
The BDR has longstanding grievances over pay and conditions. BDR已经长期不满他们的薪酬条件和现状。
