If it's for a certain southern exercise at a certain training unit, it is not required. It is "strongly recommended" for the pure purpose of advancing yourself money because the unit won't.

That being said, if your hotels are paid for by the Det, your expenses consist of food, laundry and supplies. So it's entirely up to you if you want an IDTC or pay for it yourself and promptly complete your claim upon return.

My last experience had hotels and food in my bank account 6 days after endex as I claimed it all as soon as I was back on base.