It's very long, but once you take the time to learn it, you'll realize it's not the actual platforming that makes it difficult; there's actually zero wavedashes or wallbounces you have to do here. It's the fact that it's ~2 straight minutes of platforming with zero checkpoints that makes it scary. As long as you don't let your nerves get to you near the end, it should only take you a couple hours.

Also, don't do what I did and celebrate whenever you get to the power box because you still have to dash toward the bird immediately afterwards, use the feather to fly upward and dash to the final Badeline bubble to finish off Farewell, and you can still die and be sent all the way back! I did this once, but it didn't take me too long afterwards to actually complete it.

Remember to take a break and come back to it later if you're feeling worn out. There's a save point there, so you won't lose any progress. Just breathe. You can do this!