10 seconds is a good balance between seekability and gains due to B-frames, for normal movie content. If the movement is particularly absent/easy to compress, e

10 seconds is a good balance between seekability and gains due to B-frames, for normal movie content. If the movement is particularly absent/easy to compress, e.g. with screen recordings of Minecraft (as long as there are not too many particles around), one benefits from a much larger GOP, towards the minute and even over a minute. Though you pay for this with most of the seeking you could do before. Choose wisely depending on what it's for.