Chánggōng yí gàn jiùshì yì nián, duǎngōng zhǐshì nóngmáng shí lái bāng jǐ tiān.
A long-term hand worked a whole year at a time, while a day labourer only came for a few days in the busy season.
Tips
usage
长 is 'long' here, not zhǎng. The opposite is 短工, a labourer hired by the day or the season. 当长工 is also used figuratively, for working tirelessly in the service of others.