It doesn't take me very long, maybe 15/20 minutes. The more I load the faster it goes. I started floating my tops after doing my first few quilts, this alone cuts the time in half because you just lay out the batting and top 0n top of the backing which is loaded/pinned to the leaders. I pin these with about 10 pins to the backing. Then sew with the longarm around the edge to secure it. I sew the edges and straighten the top and batting with each advance. I also find I'm using fewer pins (maybe half as many) to attach the backing to the leaders with no difference in results.
Once the quilt is rolled it's not going anywhere!