If well maintained, modern jets have a safe working life of some 30 years, but older planes will inevitably be less fuel-efficient than the latest models.

维护得好的话，现代飞机可以安全服役大约30年，但是老飞机不可避免地将会比最新款的飞机油耗更没效率。

youdao

And if you spend more than your safe spending rate in retirement, you will not have any working years to recover.

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