The only “trick” I’ve seen (thanks, Clare!), is possible once you have two receivers (after 1 year warranty ends, get the second one, but save the still-working first one). In that case, keep the startup-time on each on a different day. Even if you actually change sensors (rather than just stop/start one), most of the time the receiver that overlaps the start time will continue to report fairly accurate numbers, while the other one starts up.
Note, this is not recommended by Dexcom, and the accuracy is certainly not guaranteed, but I usually see good trend information and most of the time, I see accurate results – and have a bit more peace of mind during the startup time.