How long can you leave Italy with a long-term residence permit?

Normally speaking, departure time should not exceed 6 months. Otherwise, the customs has the right to refuse entry. But basically the customs is not very strict on this and rarely enforces it. My boss's parents hold a two-year residence permit. After taking out the residence permit, I returned to my country. When the residence permit was about to expire, I extended my residence permit. I left for about a year and a half, and it didn’t matter whether I entered or exited the country.

And it is rare to hear news about Chinese people being refused entry because they have been away from the country for too long