I think the experts say 6 to 8 years, but if you don't drive over 60 mph, I wouldn't personally worry about it unless the tires showed excessive cracks or a tire technician saw problems with them.
depends on what always parked means, you said that you did 30,000km if that is weekly driving or so, they are probably okay, if it really did just sit they should be changed as they get flat spots.
Hello there - rubber can deteriorate with age and split. So, it is best to get your tyres checked at a garage. They will advise you. This is the best way to deal with this as you are talking safety here as a matter of prime importance. Some garages do not charge for checkups Best wishes.