Your return time will be schedule
for you at 2:45 to 3:00 hours before your flight departs.
Chances are you would not be allowed on an earlier bus (I've seen DME passengers who tried, turned away).
If you choose to leave your resort any closer to your flight departure time, you will be responsible for your own transportation.
You will not necessarily spend a lot of time at the airport, and most assuredly not a lot of wasted time (at least not attributable to DME, but that's a story for another time
Depending on where you're staying, your bus needs to load the passengers from your resort and then possibly pick up passengers at one, two, three or even four (unlikely but possible) other resorts. This time has to include loading luggage under the bus for passengers not flying participating airlines.
You need to allow time to get to the airport. What if there's an accident? What if there's just a lot of traffic?
You need to allow time for the bus to drop off passengers at two or four stops around the airport, and for the bus driver to unload luggage at each stop.
If you're flying a non-participating airline, you need to allow time to check in for your flight.
You need to allow potentially MUCH time to go through Security.
Please understand, when I say "you", I mean all DME passengers and not you specifically. But DME serves a large number of Guests and can't provide the individualized service some Guests may need/want/prefer/expect.
You (this time the OP

) might want to look into a car service or cab for your return to the airport.