Yes both were elderly retired and I would guess wealthy.
But that was a coincidence
I've also booked today 2 EOT Cleans for young couples and a terraced house (living room and up the stairs) which from the address would make me think they are Not high earners.
I would describe the customer you describe as the cream of the market, but this is a sustainable market .... People will always get older and become rich
The other end of the market will always be there as well.