It's complex Elegran.
It partly depends on the purpose of the clothing - for example, if I have bought a pair of technical trousers to go walking in, there's no point in saving them for 'best', but simply wear them the next time I go walking. I may feel that thrill of wearing something new, but I don't feel particularly fetching in them and it certainly doesn't bother me if my friend's dog jumps up at me leaving muddy paw marks everywhere.
Conversely, if I buy a dress primarily to go out in for a special occasion, it will still feel new and special some years down the line, especially if it hasn't 'dated'.
I suspect however your question really applies to the genre of 'smart casual' - the concept of which I am still struggling to get my head round.
It's these items - smart shirts, edgy knits, trousers other than jeans or tracksuit bottoms, casual dresses - that seem quite presentable to go out in for a while, but when you know yourself that the 'cost per wear' has been greatly reduced by the number of times you've worn them, you find yourself thinking, for example prior to a Gransnet meet-up, 'Oh but I can't possibly wear that old thing again', although the garment might be perfectly OK in which to entertain one's neighbour for a cup of tea.
So it's a combination of purpose of garment; age of garment; and occasion on which garment will be worn.
Cost is also a factor - a £4 t-shirt from Tesco will perhaps be viewed as 'old' more quickly than an expensive dress.