Thanks ymsin, this is the input I was looking for!
Arthur2k, there are two firewalls, and the only deterioration I found visible on the outside of the hoses occured on the engine compartment side of the outer firewall. Therefore, I did replace the one hose which passed through the outer firewall, but it was accessible from above, in the inter-firewall region. Definitely locate the car where you can latch the hood in the full vertical position for this job.
There was one small hose located entirely in the inter-firewall region, and I did not replace it. I WILL keep my eye on it, because it turned out all the hose deterioration was due to oil in the coolant from a head gasket leak. That has now been repaired, but even one of the NEW hoses failed in a short time due to the oil.