FWIW I upgraded from +423 to +44 back in early August. My Balance messages now read: "Account type Personal, Balance $xx.xx -
No expiry"
It's possible that was a one-off thing for those who switched over early. I haven't recharged the phone since so I don't know if the expiration date would get set to a specific date if I did.
As for the value of credits to the MNVO, of course they'd like to "encourage" people to use up their airtime so that they can sell them more, however, as long as the cost of providing service keeps dropping then ISTM having use of our money, even if it shows as a liability on their books, is essentially an interest-free loan. That's a lot less than what they'd have to pay to borrow money for on the open market
