William,
The subject of purging is obviously personal preference. I like to work as efficient as possible and minimize the steps and time it takes to go from A-Z. Memory over the years has become relatively inexpensive to the point that to me, it's worth having the unused samples in memory versus taking the time to load, dump, reload, dump, reload, dump, etc. it.
Also, my workflow when composing is I look at a piece in sections and create all the tracks for a given section. I get it sounding pretty much the way I want it before moving to the next. It is the way I've always done it. I can hear the end in my mind but I only work one section at a time and therefore make many tweeks along the way.
I suppose if I was just plugging and chugging notes in the sequencer from a prewritten score one instrument at a time, then the purge things wouldn't be such a big deal. Input the whole instrument part, purge and on with the next. That's not the way I compose and therefore requires me to reload all samples back into every instrument for every part, for every section I work on. There's other technical issues I have had with the VSL VI purge in the past like the instrument purging samples that shouldn't have been purged after I had it learn and then requiring a reload and purge again. Just didn't want to have to deal with that.
I guess I've never thought of it much until you asked. Because of my preferred workflow, buying a big machine with lots for memory and speed so that all instruments are at my fingertips when I want them is very important. It is a left-right brain thing. When I'm composing I try to stay away from the tech stuff as much as possible because it begins to hinder the creativity..... I want to only think about the music and not the computer and software. It's time to move into the 21st century in how we use our computers. The Kontact Purge Things was great in the 386 days -- not so great today....
I feel like I just went to confession......
Hope this helps to understand my viewpoint.
Take care....