With a Panasonic code like that you would hit the maximum length of Pronto Hex (that a Pronto NG will accept) long before you could extend to a duration that would do you any good.
Most of the Panasonics are unusually tollerant of extra delays between frames in a long signal. With an older Pronto you can extend a Panasonic signal by just aliasing the signal a bunch of times into a sequence. The Panasonic device just ignores the extra delay per sequence step that the older Prontos insert.
The NG Prontos insert an even bigger delay per sequence step, probably too big even for Panasonic, but it's worth trying.
If aliasing a sequence of the above signals doesn't work, another possibility is aliasing a sequence of a slightly modified signal:
