PG_XLOG How long to retain

Being fairly new to postgresql, I have a couple of questions on pg_xlog 
We are on 7.2.1

1.  How does one properly administer the pg_xlogs?  -- How long to retain
them?
     Is it ok to delete them after a period of time?  If so, what period of
time?

2.  I understand that the numbering scheme does not wrap around -- is there
a way
     to set the numbering scheme back to 1?  we are still in testing mode,
and our
     xlogs are up to:
-rw-------  1 pgsql  pgsql  16777216 Jun 12 17:03 0000000900000097
-rw-------  1 pgsql  pgsql  16777216 Jun 12 16:57 0000000900000098
-rw-------  1 pgsql  pgsql  16777216 Jun 12 16:56 0000000900000099
-rw-------  1 pgsql  pgsql  16777216 Jun 12 16:56 000000090000009A
-rw-------  1 pgsql  pgsql  16777216 Jun 12 16:58 000000090000009B
-rw-------  1 pgsql  pgsql  16777216 Jun 12 16:57 000000090000009C
-rw-------  1 pgsql  pgsql  16777216 Jun 12 16:57 000000090000009D

3.  There is normally only 7 of these logs on our system -- so I am assuming
that
     "something" is deleteing them --  Is there an option to "not" delete
them, until
     I want to delete them.   

If there is more documentation somewhere on these questions, please point me
there.

Thanks
Pam Wampler