once installed virtually maintenance free 一旦安装几乎免维护
once maintenance
一次维修
以上为机器翻译结果，长、整句建议使用 人工翻译 。
His mechanics now take each plane apart once a year for heavy maintenance.
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This involves getting shots of tiny amounts of the allergen in escalating doses, usually once a week, until you reach the maintenance phase, when you'll need one shot every month.
CNN: Finding relief as spring allergies rage on
And once these sales are made, the customer becomes low maintenance and recurring.
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