Well, the main reason my speed has dropped is because the new season started and I picked up far too many shows =p But yeah, I was never really expecting to keep up a super-high pace indefinitely.
I blasted through Futari wa in a single week because I started it at a convenient time when I wasn't watching too much and didn't have anything else pressing to do, plus I was on the high of starting an all-new series. Also, I knew Max Heart was coming up next so I wanted to make sure I built up the momentum to push on through that.
Then I blasted through Max Heart in a single week because I knew it was a big low point in the series, so I wanted to get it behind me as quickly as possible.
Then I slowed down a bit for Splash Star because it was just plain fun and I wanted to take my time and enjoy it. Plus there was no way I could keep up the breakneck pace I'd used for the first two series for much longer either way >.>
And finally, we come to Yes!, which is maybe not quite as fun as Splash Star was, but I'm definitely enjoying it. My pace has slowed significantly for this one partly because I've run out of steam a little, but mostly because I've got so many other things to watch, due to the new season starting, plus I have other stuff taking up my time like new games and light novels (right now I'm reading the Bakemonogatari novels, which is also the new season's fault, but even if I wasn't, I have the new Accel World novel to read and various other LNs in my backlog.) At any rate, I don't want to burn myself out on Precure or anything, so I think it's a good thing if I take this one relatively slowly, but I don't want to lose all my momentum either, since I do have a full 100 or so episodes of these characters to get through!