Do you ever play with them? My "peak-Rubik" was probably 2001. My favourite was the 5x5x5. I used to have a 15-minute bus ride to work, and it took about 15 minutes to solve, so it filled the time nicely. I must have solved it about 500 times then, but rarely do so now. Last time I tried, months ago, I struggled to remember how to do it.