Sanding taking forever

Spent most of the day yesterday sanding one room. It's taking forever! When I picked up the sander, the guy said I could probably get all 5 rooms done in a day if I kept at it. I still decided to rent for 2 days anyway (I had assumed 4). Well, the papers gummed up horribly, even after I removed a lot of varnish. One room is now down to bare wood, so now I can work to get the scratches out.

Spoke with HD about the sander, and they said it really shouldn't take this long, but there must be a lot of build up on the floor. And I would just have to sand through it. When I went to pick up a bunch more sandpaper, I asked about when I would need to call to reserve another day, the guy said I shouldn't need to. Haha - apparently they don't know me very well! I am still sticking to my assumption that the floors will take 4 days. Unless something unusual happens today and I get through the other 4 rooms.