A couple of years ago, I interviewed Robin Goodwin Nordli, a veteran actor of the Oregon Shakespeare Festival, for an article that I wrote for the Oregon Arts Commission. I asked her if the actors had some sort of tenure at the festival. She replied that they did not have any tenure. Every actor has to reaudition every year.
I know that some of the actors have purchased homes and raised families in the Ashland area. They are the ones that are good enough to keep getting roles at the Oregon Shakespeare Festival or they have to find a job somewhere in the community or maybe they got a few good gigs doing commercials or films in Hollywood and returned to the Ashland area. In any, case none of the actors at OSF have tenure.
I raise this matter, because some people still seem unable to get over the fact that some longtime members of the Oregon Symphony lost their jobs. Orchestras are run differently than acting companies, and continuity of sound is an important thing to consider. You could try to reaudition all of an orchestra every year, but that would be maddening. As per the comment below, from the Oregon Symphony's principal violist, Charles Noble, that orchestra's musicians do have tenure. It is granted after a two-year probationary period. After tenure is granted, there is a formal process for non-renewal of a contract that must be followed for a musician to be dismissed. I had originally thought that none of the orchestra members had tenure and that any orchestra member can be replaced, abiding by the musician's contract and union rules. So, I stand corrected in that matter.
Even though the Portland Symphonic Choir is not a full-time professional arts organization like the Oregon Symphony or the Oregon Shakespeare Festival, its members have to reaudition every two years. I think that this re-auditioning process helps to make the choir sound better.