If you are using native Perforce replication, rather than icmrep, you can use the following two commands to check the status of the replication. Both commands should be run against the replica. They will report on the status of journal and archive file replication, respectively:
$ icmp4 -u icmAdmin -p pull -lj Current replica journal state is: Journal 16, Sequence 4823481. Current master journal state is: Journal 16, Sequence 4823481. The statefile was last modified at: 2014/02/07 07:57:04. $ icmp4 -u icmAdmin -p pull -ls File transfers: 0 active/0 total, bytes: 0 active/0 total.
If either of these commands consistently report lag, please contact IC Manage support for assistance.