At this point I can't go down in the basement without two little voices chanting "Suprise toys!" at the baby gate. This is the result of our toy storage system.
The picture above is from a couple of years ago, but it's still pretty much the same. We keep toys in marked bins like "Vehicles,"Books,"Instruments," and "Stuffed Animals" and store some bigger items on top in our basement storage room. When I notice toys have lost popularity in the playroom, I swap them out for "new" ones from the basement, typically during naps. When we get an influx of new toys, we store the majority and bring them up as "surprise toys" as needed. Christmas lasts a little longer that way. Even older, played with toys get the kids all giddy after they haven't seen them for a while.
This little system has been working really well for us. Yesterday when I ran downstairs for a candle, I grabbed a couple of stuffed dogs. I felt like a celebrity on the red carpet as I came up the stairs.