@ J- The best thing to do would be to build your Arty in cities without
Barracks- since they are not Veterans anyway, and use your Barrack cities
for regular military units. Sometimes they will be the only thing you might
need in a already barracked city- other things may take too long- so go
ahead and build them

. You will find that you can never have too much
Arty anyway so build them, build them and build them some more

.