Seems like the wrong approach to me, because in practice you really need

a reasonable expiration date or some way of determining that whatever you are paying

is still around (I still get random transactions to the Bitcoin Faucet's old addresses).

See the discussion from January about extending the payment protocol for

recurring transactions:

  https://www.mail-archive.com/bitcoin-development@lists.sourceforge.net/msg03823.html

"Give them a single token" == "give them a recurring PaymentRequest" in my mind. Or maybe "Give them a URL where they can fetch PaymentRequests whenever they need to make a payment" or maybe "Give them an array of PaymentRequests for the next X days/months/years of payments."