I agree you dont always have to and you can only do it every 4th deployment anyway so dissipate isn't going to be up each time.
90s 180s 270s 360s for deploy
120.........240s..360s for dissipate
regarding the MP loss with 3 aether stacks you get
energy drain x3 for 3600 MP vs
summon for 2400 MP
so I wouldn't call it an MP loss at the very least it's just a hassle if you have to hardcast it. however you can call it a DPS loss since you will be casting summon instead of Broils.
the 3 aether stacks also count towards your fairy gauge if you can wait 20seconds and summon your fairy again) and also your aether trait
