I'm lucky in that I'm only using 4 systems, and 3 of the 4 have the same user ID. Not sure why they decided to change it for the 4th, but alas, so sayeth the government lords. I'm able to have the same password, that I choose, for 3 of the 4, so that isn't too bad either.
But, I ALSO have to log into about 10 different online databases, analysis tools, and community pages. And each of these, because they are created/maintained by some different entity, have different password requirements. Like you, the 2 or 3 that I use daily are no big problem, but the others that I only use occassionally, are a pain in the ass.
So, like you, I have a little cheat sheet with all of my passwords on it. I hate having to do it, but after I got locked out of a couple of the tools, and had to call "somebody" to get it unf*^ked, I have resorted to weak security.