If the tire is more than 4 years old I wouldn't use them personally. Yes tires can dry rot and become hard as rocks, which would be safer? Probably neither
The best bet is to get some Pep Boy all season tires. There is a proper way to store tires if you are not going ot use them for awhile.
__________________
Sponsored by: KAM Racing Sports, Falken Tires, Progress Technology, Brady's High Performance, Taggart Performance Engineering, Rotora Brakes
Autocross is: 90% driver, 5% car, & 5%
CRAZY MOJO!
Autocross Help Page