I really don't believe infinity durability is possible outside of a JTag or ISO. The problem is that when you hex this information, it reverts to 0 durability after one use.
In this image, I've highlighted the weapons name. The Hex circled in red is the melee weapons durability. The 4 bytes before it circled in blue are the amount, and the black is the damage/stats, etc.
Same thing here but this time, it's a rifle. The condition here, "BF 80 00 00" means infinite; naturally because it's a firearm and can't break down. The amount noted before it is different this time because i've modded the ammunition being that this is a gun. The 'BD 94' is what I use on the damage/stats for all my weapons because it give them an orange rarity and pretty decent damage. I'm very curious to see if Jappi has found out some sort of pattern or info to these weapons statistics.
EDIT: I forgot to circle 4 bytes and instead circled three in blue. The 'A5 90' are the damage/stats. Please excuse this error.