I expect the default is much longer than .01 seconds.

Most IR signals have a repeat pattern around .1 seconds long. So a duration less than .1 seconds probably wouldn't get you beyond the minimum possible duration for the signal.

I assume the Pronto still obeys the repeat pattern. For example a protocol with a simple .09 second repeat pattern would permit a .09, .18, .27, .36, etc. duration. It wouldn't permit an arbitrary duration. I assume that if you ask for .25 in such a protocol, you'd get .27

My rough understanding of the old firmware is:

1) If the IR signal is the only action on a button, then the duration depends on how long you press the button. The only minimum (for a really short press) is the one-time part of the signal.

2) If the IR signal is one of two or more actions (including when you just add a tiny delay as the other action), it has a fixed (in the firmware) duration that has changed from version to version, which in at least one early version was too long for many devices and in all versions has been too short for many devices (no one duration is good enough for the range of devices).

How does the new firmware act? If I understand the earlier posts in this thread correctly, the new one has a default duration that is longer than the fixed duration described in (2) above.
Can you reduce that on a device basis for devices that were problems when (2) was longer?
Can you reduce it on an individual signal basis?
I assume you can increase it on an individual signal basis (since most of the complaints leading to creation of the feature were specific commands needing very long duration).
I assume it is the fixed duration when a signal is one of multiple actions. Is it also a minimum duration when the signal is the only action? (Duration is the longer of that minimum or the actual press)?