Other collocation considerations:

number of nodes in a storage pool mater and number of tape drives
matter - migration takes longer because you mount more tapes

if copy pool is not also collocated, reclaim take longer because more
onsite tapes have to be mounted to reclaim a given tape

if copy pool is collocated and nightly backups do not mostly fill a
tape per node, you will daily offsite reclaim as many tapes as you send
offsite

collocation make a TREMENDOUS difference in restore times of servers
(as opposed to individual files)

DR can be a real D if data is not collocated