I didn't bother with a ST until we moved into the new DC and went all-seater (but I've never managed a full season of games due to hols, work etc.) however there are definitely peeps who have their season ticket for longer than me, who have a higher number.
I'd assumed it was due to my actually buying tickets in advance, when we had that period of selling out the old DC, after Wembley and thus having a customer number.
Didn't know there was a previous thread, sorry DJ.