It is vital for us. You just need to determine if your kids will need a break, or you adults as well.
We go in the summer and leave our room by 7-7:15 with breakfast eaten in the room before we leave. We also stay in the parks until closing so taking a break/nap in our room is vital for all our sanity!
We shut the curtains and are in complete blackness for about 2-3 hours. Then we shower and return to the park at about 5.
I remember the first time bringing my oldest. It was probably around 8pm in the MK, she was in her stroller, happy/content and surrounding me all I heard was crying kids. I was so thankful we took our break and my kid was happy and. It crying!
I have always taken a break, even growing up, as a teenager, but we swam. I tried the pool with my oldest in her 2nd trip while my son napped but she passed out in the stroller in Epcot at about 6:30. I was so afraid she was not going to sleep that night but thankfully she did. After that she didn't get pool time.
We have designated non park days during our trip so they get to sleep in and spend the entire day at the pool.
But you know your kids, my 15 yo (oldest) still needs her sleep. My 13 yo, can live with little sleep, meaning he isn't crabby and my youngest can go a day with little sleep but then it catches up to her and she needs rest.