This is embarrassing. On reading drron's reply and thinking 'my flight time is neither of those', it dawned on me that i'm actually flying Finnair not QR! I booked some time ago and have been fixated on the QR lounge. In the process I've somehow conflated the lounge with the carrier. Apologies all - I'll take this to the Other Airline's forum. The responses have been very helpful (eg, Finnair also opens checkin 4hrs before)