Or other miniscule leak paths

Mine is over 15 years old now (I've had it for over 8 ). No change or top up of refrigerant has been required. Don't always run with the A/C on but occasionally switch on, just to ensure compressor seal doesn't "dry" out. 'If it ain't broke, don't fix it'! Previous cars:
S-Max 2007-2013 (only diesel I've had, good car but expensive when diesely bits go wrong, so what's the point?)
Galaxy 2001-2007
Mondeo Estate 1997-2001
Sierra Estate 1993-1997
Uno Turbo 1987 -1993
Fiesta 1984 - 1987
Fiat 127 1982 - 1984

Mine smells on start up , think it needs a service .

Just get yourself an aircon bomb from a motor accessory shop. You close the windows, put the aircon on full cold and recirculating air, set the thing off and close the doors. It kills the bacteria in the evaporator that makes the smell. Should be less than £10.

Like https://www.amazon.co.uk/Holts-Air-Con-Bom...amp;sr=8-5 BMW i3 Electric Car
2012 Full Fat RR 4.4 TDV8 (now gone)
2006 VW Touareg 3.0 TDi V6

Aye , did that last week with a new filter, still doesn’t smell 100%