Still, it's a little odd that I got away with 36000 with no 'L' but I didn't get away with 10 * 60 * 60.
Well, 36000 is > 32767 which is the largets int you can have, so gcc probably just assumed it was a long since it wouldn't fit in an int (this is just a guess on my part).
I tried this in a regular program and it worked fine.
The size of an int vs. a long int may be different on a different architecture. Your computer most likely has ints and long ints the same size (32 bits), whereas the AVR has 16 bit ints and 32 bit long ints.