I tend to see the stack of putters as the common trend in MN. If you go with only 2-3 you are waiting an annoyingly long time to retrieve.
No I wouldn't. I have zero qualms about retrieving my discs before the stack o' putters guy finishes. I'm not there to watch him putt, I'm there to get myself prepared for my round.
I warm up for a round with the discs I'm going to be carrying for that round. I'm not dragging a stack out of the car just to warm up and then have to put them away again before I start my round.