I must be atypical. The first 3 years I did PL, I used almost a whole kit each time (cherry, cobalt, amber) as I did a roughly photo a day approach and wanted consistency throughout the entire album. Most of the "leftover" cards have been used in other traditional scrapbook pages or in cardmaking. Usually I could find a way to use the back side of a design I wasn't too keen on.
I used PL digitally for a travel album and stuck to one core kit for that (plus a diff type of freebie that matched well.) Again, I was wanting a consistent look to this whole album. There were probably a bunch of digital cards I didn't use but they don't stare at me saying that I spent money on something I'm not using.
This year I am using the collect app on my phone, design f and minimal bh products as I like the square look! It is not strictly daily but roughly weekly - can be up to three pics from one day and none for others. Mixing it up.
I have also bought other PL kits to use in freer scrapbooking and I doubt I will use up all those cards!