Well, it depends.

I got a CJO in 2010, and was told to expect a class in early 2011 after I retired. Then in late 2010, I got the news hiring was frozen until further notice. At that point, I believe there were only ~10 of us in the pool. Initial words were that our CJOs were extended and hiring would start again in a few months, then next year, then "hopefully soon." At the 12 month point, AK told us our CJOs were expired but we had guaranteed interviews whenever hiring restarted.

I ended up re-interviewing in late 2013 and starting in 2014.

On the very plus side:
- When I was offered a follow-on assignment, I called the hiring desk to make sure the plan to start in 2011 was still on track. Hiring lead's (pre AK) words: "Take the assignment. We will take care of you." I took the follow-on and had a paycheck the next few years. Some did not.
- When the hiring freeze announcement was made, we were given some instructions (including maintaining 100h/yr) to stay viable. We also were encouraged to call or email if we had questions during the freeze. I did both several times at career decision points, got straight answers, usually directly from AK, and never was treated as if I was bugging them.
- AK sent out quarterly updates to the pool. Sometimes they were hopeful, and sometimes they essentially were, "we don't know when it will start again." Good comms are good.
- When hiring finally started, they kept their word and offered me an early interview. I didn't sweat nearly as much as I had in the previous one.
- I wasn't the plug for 3.5yrs.
- When I got on property, the follow-on effects of Delta's failure to restart hiring early enough meant rocket-ship (rocket surgeon?) seniority progression and green slip availability out the ying-yang if I wanted it. I grab one every other month or so, when it fits my schedule, but some folks my seniority and below are pulling down some very impressive W-2s.

Lessons learned:
- Communicate early and often.
- Always have a plan B, or at least enough margin to give yourself time to make a plan B.
- Just because you like the company you work for (and I do) doesn't mean you have to feel bad when their decisions work out to your advantage at their cost.