Finally finished all of the bosses in 5-2 on Cross Edge, which means all I have left to do is synthesize equipment (big chunk of time) and quickly run through the game once more to get two more items that I missed on my first time.
To give you a sense of how long it takes to synthesize the ultimate weapons in Cross Edge, it probably takes like 30-60 minutes to do one weapon and there are around 34-35 ultimate weapons. I have two done so far (well, three but I need an item from one of the titles), so it will take me a good while to get the rest done. Also, I will need to synthesize a bunch of the lesser weapons over to get the items you get from converting them.