If we can equate "tedious" with "difficult" then some mathematical proofs can have a very large number of special cases such as Hale's proof or Kepler's conjecture: http://en.wikipedia.org/wiki/Kepler_conjecture
Following the approach suggested by
Fejes Tóth (1953), Thomas Hales, then
at the University of Michigan,
determined that the maximum density of
all arrangements could be found by
minimizing a function with 150
variables. In 1992, assisted by his
graduate student Samuel Ferguson, he
embarked on a research program to
systematically apply linear
programming methods to find a lower
bound on the value of this function
for each one of a set of over 5,000
different configurations of spheres.
If a lower bound (for the function
value) could be found for every one of
these configurations that was greater
than the value of the function for the
cubic close packing arrangement, then
the Kepler conjecture would be proved.
To find lower bounds for all cases
involved solving around 100,000 linear
programming problems.
When presenting the progress of his
project in 1996, Hales said that the
end was in sight, but it might take "a
year or two" to complete. In August
1998 Hales announced that the proof
was complete. At that stage it
consisted of 250 pages of notes and 3
gigabytes of computer programs, data
and results.
