Max GOP?

[rumplestiltskin]

I understand (somewhat) the concept of the GOP. I'm unsure, however, of how (or even if) I should alter the default setting.

As a specific example: I often encode H264 for iPod from AVI source material. I try to keep the size of the frame as close to the 76,800 pixel limit (using the "rule of 16's"). Then I drop Qmin to 3 and Qmax to 28. This improves the quality of the video dramatically. However, what (if anything) should I do with the Max GOP size setting? The default seems to be 250. Should I make this a smaller number to improve quality? If so, what would make a significant improvement? Is there a downside to doing this? I'm not expecially concerned about increasing file size as the Q:2-28 does this already and, for my purposes, I can live with that.

Any suggestions appreciated. Thanks!

[Case]

AFAIK the max GOP size is the maximum number of frames from I-frame to I-frame, the same as the number for Keyframe with other encoding engines. It doesn't effect quality directly, it does have an impact on filesize. However, the refreshing effect of I-frames may wipe playback artifacts, so the viewer may perceive more quality with a smaller GOP size.
250 is already a lot. MPEG-2 has 12, DivX often has 240. For NTSC Film (quite common) 250 means 10.4 seconds of frames depending on each other! Most scenes don't even last that long, and an I-frame may be inserted automatically long before that.