MIG wrote:

Non-Oyster Underground fares have been put up punitively, but if you
live near a National Rail station you don't have the option of Oyster
for your travelcard. Walking to the nearest place that you can get an
Oyster travelcard on the morning when you need to renew is not exactly
practical, although it may be practical to have some prepay credit on
your Oyster to use when needed.

Aren't there the options to renew in advance/over the phone/online?

(Mind you the latter two weren't available for the student discounted Oyster
when I last tried to renew that way. I got a rude email from TfL whining on
about fraud prevention when these methods perform identical security checks
to turning up to the ticket hall in person or using the card in practice.
Contrast with National Rail who generally have no problems selling railcard
discounted tickets online or at machines...)