Dave Newt wrote:
I'm pretty sure it's not the case in my experience... For some reason,
the gates NEVER EVER tell me my season ticket is about to expire, so I
often find later in the day that I have paid for the morning's journey
using the bit of pre-pay I have on the card*. If I then renew the
season ticket, it doesn't give me anything back for the morning's
journey.
* Which is why I try to keep as small as possible an amount on the
card now. It's annoying and I don't know why I never get an "about to
expire" message on the gates. I just try to remember to put a
reminder in my phone for when it runs out when I buy a new one now.

Could it be that the pre-pay money (i.e. validity) is the reason you don't
get the warning? The logic (if this is the case) presumably being that the
card as a whole is not going to expire, so you will still be able to travel.

(Guessing. Another issue for someone who *knows* ;-)