yeh the cpu is def a factor
the Last Ever kit runs at about 18-22% cpu for me
For me it was more of a ram issue but I was about the same with 18-22% when it was running. JuanSOLO mentioned a couple times recently that Live was running sluggish for him; I had the same problem and it was a huge turnoff working in Arrangement and I think in the back of my mind I knew it was because of the 128's but didn't want to go through the process of converting the samples into one file.
My main drum kit is 8 cells, each one having around 80-100 samples. If I wanted to swap one set of kicks to another one from my browser, it took awhile, like almost a couple minutes, just to wait for the computer to do it's thing. Even just dragging in another set of samples into a drum cell would take awhile.
Also, it used to take A LOT longer to load at startup as well as each project loading when I kept the samples separate. Now it's all a breeze.
All my main kits took a day to do and I still have remaining multi-kits but I just update them as I go along or when I have some idle time. It's tedious but totally worth it. And even though it is tedious, you get quicker at it the more you do it. Really the only tedious part is clicking back and forth between the sample and inputting the sample start time, but once you get into a rhythm/zone it goes by better.