Originally Posted by
unavaca
Boo 3 hour limit

It sounds like the only thing this saves you is having to lug your suitcase onto the MRT.
It would be nice if I could check out of my hotel, drop off my bag ~11am and then wander around the city until the 8pm HKG-SIN flight.
I was able to do what you described above last September (same 8pm HKG-SIN flight). At that point in time, you could check in at the HKG airport express station anytime on the day of the flight (not sure if you could also check in day before if flight was within next 24 hours). Perhaps there was a recent policy change that restricts HKG airport express check-in to within 3 hours of UA flight departures?