2 sentences

1. 由于过了保质期，这种药已经失效了。

   yóu​yú guò le bǎo​zhì​qī, zhè zhǒng yào yǐ​jīng shī​xiào le.

   Because it is past its expiration date, this medicine is no longer effective.

   Source: Dong Chinese Dictionary

2. 我们把新鲜的肉类放进冰箱冷冻，以延长保质期。

   wǒ​men bǎ xīn​xiān de ròu​lèi fàng​jìn bīng​xiāng lěng​dòng, yǐ yán​cháng bǎo​zhì​qī.

   We put fresh meat in the freezer to extend its shelf life.

   Source: Dong Chinese Dictionary