Flex Circuits - Connectors

[Ray from NJ]

I have some questions on the FPC connectors that everyone seems to be using.
1. What is the reliability of the ZIF connectors?
2. Will the locking mechanism become unlocked easily?
3. Whick lock is better, the flip up bail or the press in?
4. Most of the connectors and flex contacts have a tin or solder finish. Should I select a gold finish for long term reliability?
5. How many times can these connectors be operated before
failure?

Thanks

Ray