and you can buy them in advance (up to 4 days IIRC) so you can hop on a
bus close to home and avoid the queueueueueues at the ticket office.

It is seven days for the one-day and weekend cards. The four days is for
the period travelcards on paper tickets (you can charge an Oystercard a
month in advance).

My local railway station would never sell off-peak travelcards until
approximately 9:25am on the day of travel (i.e. after the last timetabled
departure before 9:30am) and the ticket machines also wouldn't offer them
until quite near 9:30am. I assumed this was a widespread policy and was
blissfully unaware till this year that you *could* buy them in advance
elsewhere.