The closest I can find to official advice to 'let your bits breathe' is this paragraph from NHS direct:
Tight-fitting clothing
Wearing tight-fitting clothing, such as tights, or using panty-liners, may increase your risk of developing thrush. However, the evidence to support this is still uncertain.
Which isn't exactly conclusive, and I'm not wearing tights to bed, just a pair of cotton knickers, which I can't believe makes that much difference to air flow under a thick duvet and a pair of pjs.
Sorry if I sound like I've got a bee in my bonnet but this question comes up a lot on MN and I'm fed up of being told I need to air my fanjo when I've never had thrush in my life. As for being prim, proper and prudish, it's just a comfort thing, I make no judgement on those who find it more comfortable to go without.
(As an aside which should probably be taken to the feminist boards - is the airing thing perhaps part of the socialisation that vaginas and vulvas are intrinsically yuck and need to be freshened and douched and generally cleaned and tidied up?)