Review on Sanding Detailer Standard Kit - Coarser Grits, Pack of 24 by Benjamin Glasper

I'm renovating an old house. Lots of cleaning and sanding. They really come in tight spots on window frames etc. I especially like them for fixing wrong way sand grooves on inside corners. More effective than wrapping the spatula in sandpaper; probably because the design allows for a lot of force per unit area (psi). Strips of sandpaper last quite a long time because you can advance them a little at a time and have fresh paper. You can use every last bit of fresh abrasive. Then throw them away. No more bags of partially used (can they be thrown away?) sandpaper supplies. It solves one of the biggest problems in life. When is it time to throw away the old sandpaper and start with a new one?