A little more imformation is revealed later in the thread. The tires have spent a good portion of their lives covered up. That is a good thing & adds time to the tires usable life IMO.
5 years is 5 years but a tire does not suddenly self destruct after the 5th year. At this point, with quality tires, I'd be checking them more frequently & extra carefully & as long as the tread life is still good go for another year. If the unit is only used for short weekend trips, so much the better.
If I were to be embarking on a long multi week trip I'd be leaning more to replacing sooner rather than later.