Unless the caster actively dispelled it, a Flying Thunder God mark would remain forever.
Moreover, such marks were extremely concealed and very difficult for anyone other than the caster to detect. Obito Uchiha had carried one around for so many years without ever noticing it.
Of course, if someone's ninjutsu mastery was strong enough, they should be able to break a Flying Thunder God mark left on them by someone else. No matter how powerful a ninjutsu was, it was still ninjutsu and could naturally be countered.
Yinsen did not know whether Obito Uchiha could break a Flying Thunder God mark, but since he had not even discovered it, there was no need to mention breaking it.
After Minato Namikaze was revived, he immediately sensed the mark he had left behind all those years ago. It was quite far away, though, so he did not rush to act—Minato Namikaze was not the impulsive type. Even if he wanted revenge on that person, he first had to make the situation clear to everyone.
He then learned about everything that had happened in the Hidden Leaf Village over the years, as well as the enormous threat posed by Akatsuki. At the same time, he believed the mysterious person responsible for the Nine-Tails Attack was an Akatsuki member—information provided by Itachi Uchiha confirmed this. That person was the hidden mastermind using Madara Uchiha's name.
Under such circumstances, even if he wanted revenge, he would not act rashly. They needed to discuss a detailed plan before making a move.
It was in this situation that Jiraiya proposed personally heading to Amegakure to investigate and probe Akatsuki's true strength.
On the surface, Jiraiya wanted to conduct reconnaissance, but there were other factors involved as well. Pain, Akatsuki's nominal leader, possessed the Rinnegan, and that concerned