Hardwood floor finish difficult to sand down

Hi all.
I have 1.5" wide maple strip flooring in a 1950s-ish house.

I had planned to rent a Clarke orbital floor sander (only sander available here at the local hardware store) for a long weekend and get two 12X12 bedrooms and a 15X20 living room and a few closets sanded. It took one day just to do one bedroom, taking forever to sand off the old finish even with 36 grit. Edging with a palm sander takes equally as long.

Now two weeks later when I finally have time to tackle another room (tomorrow), is there a faster way to do this? I think part of the problem is the flooring has some very minor imperfections and maple takes forever to sand, thus the long time to sand the floor level.

I have to say though the floor is a lot smoother now in that one room I have gotten done, but I wasn't planning on this job taking so long. One guy bid the job at $1500 with two coats of poly and 1 coat sealer...Factoring in my equipment costs, sander rental and time, this bid is tempting.

This photo is the living room, which I am saving for last.

Any recommendations? Should I try 25-grit paper to start?

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Hardwood floor finish difficult to sand down