On Feb 2, 7:51*pm, Matthew Geier
wrote:

*Ezlink did once publish a study on the usage of their cards, which noted
that a larger than expected number of cards had been issued that simply
disappeared from the system. This was a source of concern as in the early
days they were subsidising the cost of the cards. Two of those missing
cards would have been those held by my wife and I. Only those reappear in
the system every 12 months or so as we transit their city. :-)

Exactly what happens with Oyster: very many rarely used (including
mine) or never again used cards [1]. But, given the very large gap
between Oyster fares and cash fares, the incentive is there to get an
Oyster card when making only one visit to London. There really ought
to be an expiry date on these type of cards in a metropolitan area -
perhaps 3 years. Maybe make them renewable until such time as the
scheme operator needs to replace them, but renewed only by an explicit
action by the card holder.

[1] Actually I have 2, the first one being a very early PAYG that the
web site refused to register even though it was still working in
practice (i.e. I could top it up at the self service machines) but I
do not use it now. A TfL office merely gave me a new one without
cancelling the old one.