I use Boge cartos all the time. And yes, after just a few days use they become hard to draw. I can see clear thru the hole, so I know that is not the issue at all. After tearing one apart I came to the conclusion that a lot of un-used juice just collects at the bottom of the filler. As more and more collects, it becomes harder to draw. One day I decided to try to detemine why they become hard to draw and tore one apart- it was a used one, hard to draw, and was "empty" as far as hitting it was concerned. When I got is tore apart, the filling was so full of juice that it soaked my fingers just holding it. I could see no other problems internally. So I came to the conclusion that it must be getting full of juice at the bottom end over time.
I always just toss them when they get to that point. They are cheap - a whole lot cheaper then buying a pack of analogs per day. So I just buy a couple boxes of them at a time, and toss them when they start getting hard to draw. Funny thing is the one I'm currently using has been on since last Friday- that's a record for me, as all previous ones lasted 3 days max. But this one is still hitting just fine. Not sure why this one just keeps going.