I used to take apart two audiocassettes
and, with a hobby knife and extra-thin adhesive tape, splice extra audiotape from one into the other to increase the runtime. Sometimes I'd selectively remove some of the plastic pegs and things from inside to fit the larger tape reels in.

This trick was very good for dubbing overly-long records, multiple albums, or long radio events onto a single cassette. I think my record was getting two full hours of tape into one 60-minute cassette.
( Rob T Firefly talked, like, William Shatner, on, Tue 5 Jul 2011, 0:03, 3 replies)

Or
you could have bought a C120 cassette.....
(greatoldone Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl f'tagn, Tue 5 Jul 2011, 8:14, closed)

not a good idea
C120s were thinner material and stretched easily
(CADmonkey rollllllllled another one, just like the other one, Tue 5 Jul 2011, 19:25, closed)

Plus
in my area shop a C120 was more expensive than two C60s, and I was usually broke anyway.
( Rob T Firefly talked, like, William Shatner, on, Wed 6 Jul 2011, 14:45, closed)