How often do I need to reindex tables?

I am planning to use 8.2 and the average inserts/deletes and updates
across all tables is moderate. That is, it is a moderate sized
database with moderate usage of tables.

Given that, how often do I need to reindex the tables? Do I need to do
it everyday?

Also with 8.2, I do not have to do vacuum anymore or that is what I
understand. Does it do auto-vacuum?

Thanks in advance
Dhaval Shah