The formula (so far) is:
Merits carried over = (merits earned last week) + (merits earned week before)/2 + (merits earned week before that)/4
With the math somewhat skewed because the first week didn't adhere to this at all.
This means that if you earn X merits every week, you will have 2.75 * X merits in total. So for 10,000 merits you "only" have to earn 3637 merits a week. Which is still a *lot* mind you.
That's 73 cargo runs of 50 merits instead of 100. 36 hours of play (assuming playing the entire time waiting for next merit allocation) instead of 50.
But there are ways around this. Here are two:
1) Buy extra merit allocation. If you already own 3 anacondas and are wondering what to do with the rest of your 1BCr stash, why not?
2) Wake up, turn on ED, receive your 50 tons of stuff. Go have a shower, have breakfast. Get another 50. Do some more stuff, notice 30 minutes have ticked by. Get another 50. Keep doing this, not shipping them, just building them up, with ED just on in the background while you go about your daily chores, getting 50 tons of merits every half hour. Once you've filled your cargo bay, ship them all in one go.