Sometimes that might be handy. But i'm online now, and I might receive
a reminder to top up my travelcard (4 days before it expires), so it's
more convenient to quickly log onto the Oyster site and transfer some
funds than it is to remember to queue up some time before I actually
need to. I'm going to check and see if these rumours of
"validators" are true and that I can simply swipe my card without
opening a gate - that would seem to be the best solution.

The validators you mention exist, they are remote and often placed by
manual gates (the big glass gates for luggage etc). They're usually
inside the gate, so you'd have to ask a member of staff to let you in
to touch on it.

It won't be a problem for you with a season ticket, but for people
using pre-pay on Oyster and no season ticket, they'd start a journey by
doing this, and end up paying at least a minimum fare, with an
incomplete journey to sort out at the ticket office (thus they might as
well have just queued up in the first place).

Its one of the restrictions of Oyster unfortunately.