What things can influence log_shipping_monitor_secondary - last_restored_latency values? Looking at msdb.dbo.log_shipping_monitor_secondary last_restored_latency values for each log shipped db.
last_restored_latency - The amount of time, in minutes, that elapsed between when the log backup was created on the primary and when it was restored on the secondary.

Usually this value is 0 or fairly close to 0.  Every once in awhile see a higher number in this column (850).  What are the things to look for that can cause high values for last_restored_latency?
Most significant variable is the size of the transaction log backup that you are trying to ship, larger files :-
take longer to copy,
longer to restore &amp;
more time to create the standby file.
If tlog backup size doesn´t explain more than 90% of the variation then you can start to troubleshoot whether server CPU or network congestion is involved.