Hi new here!
Interesting topic... But surely it's up to you how long a task is which is pretty much nothing to do with GTD? The whole point of GTD (from what i can see) is that you are going to do these things anyway - it's just a matter of tracking them better and getting them out of your head. Its the difference between going to a shop with out a list, struggling to remember what you need to buy and constantly going up and down the same aisle as you forget something - to working of an organised list where you can pick up everything with ease and as quickly as possible.
With the small actions you do them as they crop up and only write down the bigger things to put on the next action list (anything over two mins). Thats my understanding any way...