John, I use LR daily, at times only two hours, but some days for 10 or more hours, depending on the requirements. If I spend all day using LR, I'll optimize at the end of that day, otherwise once a week. I recall Jeff explaining, it cleans out all the cruft.
I understand from Adobe's announcement that the greatest improvemnt should be noticed with 12 GB RAM of more. My iMac is only equipped with 8 GB, so maybe the speed increase is minimal. I haven't yet imported with this update, but I don't really have a problem importing while washing dishes or ironing shirts. Last Sunday's import of some 550 X-Trans raws took about 30 minutes, giving me time to eat breakfast and read the newspaper.
The really frustrating time working with LR is the first half hour or so following restart of the program. A few updates ago, I thought LR had become a bit snappier, but that impression has faded. I'm patient though.