Troy, I believe you're right in thinking flags having a duration.
As to the duration, a number of factors come into play. Obviously any time delay, including the .3 second delay after the command is sent will have a great affect (I know you have already accounted for this one). We can see within Properties of the remote memory space, however, there is no information of processing speed of the remote itself, maybe someone out there knows? I feel that this must come into play at some stage.

On my own T2c, I can control a Split System Air Conditioner using a series of flags, each button push (Macro) requires roughly 16 to 18 flags to be checked and where required, set or cleared along with page flips and one discrete code to be sent.
If buttons are pressed too quickly the remote tends to lock up, so if I am demo'ing the remote (not in front of a AC unit), I tend to pause briefly between button pushes so as to not lock it up. Looks bad in front of a client!