Endurance of the Berserker Question

During the last game session, one of my player had a doubt about Endurance of the Berserker and its duration.
Reading the last paragraph of the spell, some of my player started to have doubts about the functioning of this spell, especially with the Consecutive castings delay the end of the spell - that is, put off the time when accumulate wounds take effect - part.
So we asked ourseves if this spell could be designed with a duration longer than Concentration, such as Sun. And if with a new duration it has some other "contraindications".

So ... can someone help me, explaining to me how this magic works exactly?

my take was like this since I had made a diameter duration... (i now feel this take is wrong)

  1. you get wounded
  2. cast endurance of beserkers
  3. time passes, cast it again to extend the time you ignore the wound.
    4.get wounded again
    5.try to cast endurance of beserkers again...it extends the 1 set of EoB the second wound is ignored
  4. time passes, spell expires
  5. recast EoB (with both wound penalties). it effects both wounds.

I now beleive it works like this...

  1. get wounded
  2. cast EoB, ignore wound
    3.get wounded
  3. cast Eob, ignore all wounds
    repeat until you reach the limit of size +2 castings

The line about delaying the end of the spell makes no sence since it is designed as concentration in the book.

Yes you can create a version that last longer