Do tyres (or tyres as you call em over the pond) have an expiry?

Ive read 4 years and 6 years now im thinking if the tyres been kept in a cool dry place its probably not that bad but my track bike has been stood up for about 3 years now and the tyres could look better (there a little bubbled etc) should i just change them to be sure or could i get another couple of track days out of them?

If i should change them, which to be honest, im wavering towards as is it really worth the risk? im thinking about using maxxis supermaxx sport its only a 95 CBR6 and im only inters so im thinking these might be good as i dont have alot of money to through at tyres and i already have spare wheels with slick on and spare wheels with wets so need a sort of middle tyre are the maxxis going to cause me problems over say pirelli supercorsas which are twice the price?

After the silicone layer is off the tyres the grip will decrease over time and 4 year old tyres will give noticeable less grip.
Besides that, if the bike is standing on it's wheels you'll get a flat spot where the tyre contacts the floor.

I wouldn't use 4 year old tyres on track, better to be safe then sorry.

Well mine were 4 years old with virtually no miles on when I bought my bike. ( old dealer stock) Tyres were shocking. Slipped and slid every ride. Junked em. Metzler rep at Brands Hatch said they go off. He was right.
I guess if you are really gentle you wouldnt notice.
New Michelins are great.

I bought my 08 brand new 6 months ago and the tyres that came on it were terrible, they had absolutely no traction...you'd look at them funny and they would break free.
A friend has the same type tyres and doesn't have any issues with them, so I assumed they were just old.

When I buy a new bike from a dealer I ALWAYS insist on new tyres of the brand I want as part of the deal