easy one: location of the database cluster

Hi All,

I'm in the process of putting together some docs for a new postgres server. 
For development use, I've always just been content to have the PGDATA 
directory as a subdirectory of the main postgres install directory which is 
/usr/local/pgsql/ by default (when installing from source anyway).

My question is whether there is any good reason not to do that in a 
production environment (for example upgrade time)?

Is there a "standard" directory that people tend to use for this, such as 
/var/local/pgsql/ ?

Even if there are no standards, I do like to follow conventions where they 
exist, since I don't expect to be around by the time this system will be 
requiring it's first round of maintenance ;-)

OS is (will most probably be) RHEL3

Cheers
Iain