It's not a "lifelong investment" if you plan to be an airline pilot, because you never wear those massive chunky style headsets in a jet. They've only got to last you through your piston and/or turboprop flying career.
Sennheisers are a bit fragile and Bose is just an outrageous ripoff, you really really can't go wrong with a
David Clark H10-13.4 Headset by 'David Clark' from Flightstore.co.uk , they're passive but they're really good noise reduction, super comfy, pretty much indestructible, the toyota landcruiser of headsets, give them a wash after 10 years they're as good as new.
There are always plenty of good used ones on ebay for £120 - £150