Long-running

The long-running game show has a unique format, in which three contestants vie to be the first to supply the question to an answer they are given.

Source: tatoeba (10367003)

The war between Western Sahara and Morocco is a long-running conflict.

Source: tatoeba (11728236)

The long-running play finally closed on Broadway, just short of setting a record for longest playing.

Source: wiktionary

Services on SWR's neighbour Southern were badly disrupted for nearly 40 days in 2016-17 following a long-running dispute involving drivers union ASLEF and the RMT. And it's passengers - the very people the railway is there for - who are caught in the middle.

Source: wiktionary