The phrase, many days and years, means literally, the days upon or beyond a year. This can refer to anything beyond a year, or two years, or three years, or years upon years. In every case it refers to the long duration of the event or events that are going to occur.
The vintage shall fail, is a phrase that refers to the failure in agriculture. And in general the failure of business.
The greatest part of the wealth and prosperity of a nation, is generated through business wherein the production, the buying and selling, of new goods and services all contribute to, and are a core part of, a nations prosperity.
When there is a general failure in agriculture, and a general failure in business, within a nation, then that failure leads to great distress for many people.
But, when the entire structure of business fails, then everyone is affected and all manner of physical and mental stresses overwhelm a nation.
And such is the nature of this warning.
When truth is ignored, and therefore God is ignored, then disaster is always just over the horizon.
And when people are comfortable in their way of life, and generally indifferent toward Bible doctrine, then that looming disaster will not only be the furthest thing from their mind, but that people won’t believe that it is even possible.
When a national disaster strikes, people will not be prepared either physically or mentally, to handle it.
And after a national disaster strikes and overwhelms a nation, getting back on track is extremely difficult, and takes a very long time, literally years.
And, as Isaiah’s words are directed at history in general, but primarily at the final days of history, when this disaster finally occurs in those final days, the only way out of it will be the second advent of Christ.