Not sure where you heard about changes every three days...I change when it's overflowing. What I don't get is that it use to be every 5 days or so...but now it's every 1 1/2 to 2 days. I also wouldn't want to leave it in there for "several weeks" out of fear of decomp, and releasing nitrates and phosphates back into the tank. I'd stick to the weekly changes if it were me.
I'm pretty sure that your socks, just like any filter, are getting slowly clogged over time despite thorough washings. You can never remove 100% of the accumulated matter each time you wash. I would bet that if you measured the weight each time you washed and thoroughly dried them, you'd find the mass of each sock slowly increases over time.
I will admit that I've had these socks for quite some time and that they might be doing exactly what you say. However, what I do about once a year is soak them in bleach for a day or two and rinse. After doing this a couple months ago, there was no change in the time they lasted.
Otherwise, my cleaning protocol is to run them under the sink faucet when rubbing fabric to fabric. They are seven inch mesh socks, 200 microns.
The problem for me making my own is that I need the plastic ring.
And what fabric do you buy???? nylon mesh??? with micron size??? I apologize, I'm ignorant when it comes to purchasing fabric.
@AllSignsPointToFIsh , so you got me......I just ordered four new socks. Let's see if there is a difference.
Experiment Day!
So
@AllSignsPointToFIsh forced me to buy new socks.

I purchased 4 new seven inch, 200 micron socks from a vendor on Ebay. What I liked about this purchase was, not only were they fairly priced (5$ each/free shipping), but they were made in the USA! When is the last time you purchased something for your tank that was made in the United States?
So the thought was that my old socks, requiring to now be changed every 1 1/2 to 2 days, were clogged with some nasty stuff that my yearly bleaching wasn't cleaning out. I use to get 4 - 5 days out of each sock. So has my tank changed or are these old socks clogged?
The new socks arrived today. Now the one variable is that these are a different brand then what I've been using, but otherwise they are listed as 200 micron....the same size as the old ones. Here's the label on the new socks.
They appear to be the same size and shape of the old socks (New on the left, Old on the right).
However, the one noticeable difference is that the new socks are more transparent/less translucent. Here are two pictures looking through the old sock and new sock, respectively, of the window in my house.
New sock went into the tank at 1PM, 2/23/16. I'll update and let you know how my little experiment works out.
In the meantime, the difference in transparency bothered me, so I took one of the old socks and I'm soaking in vinegar, thinking it's clogged with inorganics and not organics, which would have been "consumed" by the yearly bleach bath.