I also do rotating boxes. At the moment we have the Kung Zhu hamsters, lego and scalectrix out (ie in the hidey behind the sofa, so within easy reach). Maybe next time we'll have the nanobugs or the railway or the cars... who knows!

We have a lot of lego, so we'll swap around various sets of lego.

I also chuck out a lot. I'll keep the "good" stuff (the duplo, brio, baby play mat, wooden activity cube... - well, we'll have grandchildren some day) and get rid of the cheap plastic stuff to a charity shop. Or the bin, if it's broken. How sentimental can you get over a toy? Yes, a favourite soft toy or some expensive bits of lego/brio, or the odd toy from a now-deceased relative, but the most sentiment I have is over the big items I wanted as a child that I buy for Liebs (the lego and the two-story shed we're getting this summer so Liebs can have an outdoor sleepover!).

Can I ask why the toy is sentimental? Thinking about this may well help you decide if it does need to go or not.