So often, but not that often. Do you want to hit RnR more then once? More then one day? If so you need hoppers, personally i love hoppers, i like to eat at Epcot most nights. So i always have them.
Park hours aren’t officially out yet, but I checked touring plans and Kenny the Pirate and the 16th I would do Hollywood studios and Epcot (you have park hoppers and you the trip is for RnR). You can take the boat or walk between its your arrival day so i think if its for RnR you def want to get that in. I also think HS doesn't have enough for a full day but that's just me (Toy Story land will be open, so I would guess HS will be crowded every day and if you want to see Toy Story land I would try to FP on your last day) . Maybe after head to Epcot for dinner and to do your favorites.
The 17th I would do full day MK, Depending where your staying take a mid day break or do a TS lunch to get out of the heat.
Then the 18th I would do Animal Kingdom and HS another ride on RnR, and see your favs in Animal kingdom.
If it was me, we would only do 3 parks, or do one park with reduced time which is what i have here for you with Epcot, 2.5 days is not enough time to really do all 4 parks well, so whats the priority. That's how I plan at least, I say I must do xyz this trip make sure I do them and everything else is gravy.
For the last day it really depends what time do you want to leave to get a 5pm flight, 2ish? So you would need to be done wit the parks by 1 to get back to the hotel, are you taking DME? We used to do park days the last day but stopped but that's just us. We take an easy morning get breakfast any last minute shopping, this trip we have a 3pm flight and will plan to head to the airport about 1230, it just didn't seem worth it to me to add a day.