there are heavy odds in favour of our dying between the ages of sixty-five and eighty

直译：在60到80岁之间的时候，有很大的概率发生死亡。

一般意译为，我们在60岁到80岁之间死亡的可能性很大。

in favor of支持，有利于

odds in favor of 引申为：一件事情的发生的概率

odds in favor of our dying 死亡概率

在朗文词典中，odds词条里有这样的说明：

possibility

the odds against / in favor of

I'm afraid that the [odds] are heavily [against] her winning (=it is not likely) .

The [odds] are [in favour of] a Russian victory (=it is likely) .

例句：

I reported to Nixon that the odds were two out of three in favor of a rapid conclusion of the war.

我向尼克松报告说迅速结束战争有六七成的希望。

thought the odds were in favor of your murder.

我认为你有谋杀的机会