WAL segment management on a standby

Again, thanks to all to have assisted me with getting the WAL segments to both my standby servers. Everything with that
isnow working quite well. I do have a related followup  
question, however. On these standby's nothing is built in to manage those WAL segments in the archive directory. Thus,
thatdirectory can grow to the point where it fills up the  
disk rather quickly. Any good strategies for dealing with the WAL segments that get put in there. Do I really need them
afterpostgresql has copied them up into the pg_xlog  
directory? If so, how far back should I keep them? Yes, I know about keeping everything between backups. So, if my
directorylooks like: 

00000000300000000C000000A1
00000000300000000C000000A2
00000000300000000C000000A3
00000000300000000C000000A3.backup
00000000300000000C000000A4

Could I safely delete the *A1, *A2, and maybe even the *A3 files?
--
Jay