"longstanding customers" is correct and usable in written English.
You can use it to refer to customers who have had a long-term relationship with a company, such as customers who have been with the company for several years. For example, "We would like to thank all of our longstanding customers for their loyalty and support over the years."
Western nations can offer more generous financing, have longstanding customers, and offer better maintenance and spare parts service after sale.
Still, some longstanding customers say the bank will need more than that to restore confidence, especially given the broader challenges still confronting the banking sector.
That recommendation would, of course, cost the insurers money and put an end to a culture of using longstanding customers to subsidise newer ones.
Earlier in the day, the FCA confirmed that it would begin an investigation into zombie funds this summer as part of a wider inquiry into the possible mistreatment of longstanding customers.
Yet when I was growing up in a corner shop in London, my dad had longstanding customers who would come round in the evenings to keep him company in the shop.
Britain's financial watchdog has strongly criticised the way some life insurance firms have treated longstanding customers with pensions and other savings products and is carrying out a further investigation into six companies.
He said that AT&T had assured him that as a longstanding customer, he was not tied to a contract.
But it is also incumbent on us, when we do come across a problem with a longstanding customer, to trust their account of the situation and do whatever we can to put the situation right".
Blairmore was a longstanding customer of Mossack Fonseca, whose internal data was obtained by German newspaper Süddeutsche Zeitung and distributed by the International Consortium of Investigative Journalists to the Guardian, the BBC and other media outlets around the world.
SHORTLY AFTER 8 o'clock on a frigid Sunday night in early January, Dolly Lenz, one of the city's best-known luxury real estate brokers, bustled into the Four Seasons with the familiarity of a longstanding customer.
Bland soothed frayed nerves of longstanding Quark customers, increased vacation time to improve morale and sat for two hours with Apple Computer founder Steven Jobs, mending fences after Ebrahimi badmouthed Apple when it was floundering a few years ago.
