If you’re not using another buff it’s fine. Apt’s advice is specific to queuing up a large amount of materials to craft when using pies to maximize your gains.
Teaching pies don’t use a timer, but many of the food and brew buffs do. These only run down when you are active in a world. So if you eat a pie for 45 minutes of a buff and then log out in 15 minutes you will still have your buff when you return.
Teaching pies are the same in that you can log out for a long time, or do other activities. If you don’t die or consume another buff item the teaching pie will stay active until it has earned the correct number of points for you.
Increasing your character’s Zeal attribute will prolong the effectiveness of a buff. When maxed it roughly triples the duration of the buff. For a brew buff this is usually from 5 minutes to 15 minutes. For food it is usually 15 minutes to 45 minutes.
For something that works on points like the teaching pie, it means you can earn a little over 200k points with a single pie using a maxed Zeal stat - as opposed to just over 70k with no points in Zeal.