Don’t really agree with this. Getting out of the room at LM KUL, taking the lift down, dropping key in express checkout box, crossing the road, walking to Ekspres station takes 5-10 mins max. As you said, tickets can be bought beforehand and right now there’s a VISA Paywave option to flash your credit card right at the gate (look for the special VISA marked sensor). Time it right and there’s no waiting time for the train. Getting out at KLIA - there’s an escalator option that gets you up to Departures in like 3 mins. Total 45 min maybe but not an hour. Same for the other way around. Without a big bag it’s even faster.