1. old customer 老顾客
We made the new policy to attract our old customers.
我制定新政策就是为了吸引老顾客的。
2. regular guest/customer/client
语境中直接用regular也可以。
You're starting to become one of my regulars.
你开始成为我的常客了。——美剧《致命女人》
This is reserved for our regular guests.
这里专门给我们的老顾客预留了。
I saw you at the bar three times this week. You're definitely a regular.
我这个星期在酒吧见到你3次。你觉得你肯定是老顾客。
3. patron /ˈpetrən/ 主顾/老顾客
I'm a patron of this cafe. I enjoy spending time here.
我是这家咖啡馆的老顾客。我很喜欢在这里过下午的时光。
I would love to be a patron to support your restaurant.
我很乐意成为你们餐厅的老顾客。