expression
Formal or literary expression used in polite correspondence and speeches to express ongoing gratitude or patronage. Often appears in set phrases like 平素よりお世話になっております.
平素より格別のご高配を賜り、厚く御礼申し上げます。
We would like to express our sincere gratitude for your continued patronage.
平素より弊社製品をご愛用いただき、誠にありがとうございます。
Thank you very much for always using our products.