Nah. I MUCH prefer the term 'season ticket holder'. In general business terms though, STHs, 1901 Club members and box holders are all account holders. Absolute gold dust to the companies with which they have the accounts, especially if those companies are in the leisure field, where purchases...
Every little bit helps but I'n not sure that sending big-spending account customers a folded piece of mono colour card with a printed message inside is THAT big a gesture to be honest.