Finance is simple at sight, whether the question is what a dollar will be worth sometime in the future, what a dollar sometime in the future is worth now, or what the net present value is of an income stream extending far into the future. There are assumptions and unknowns, of course, most of which we can estimate from past experience, if only roughly, and if only assuming some similarity between past and future, but these are the kind of assumptions we must make whenever we approach the future. The predictions we make can be informed and weighed and even reasonably accurate where we are concerned. Without some semblance of predictability, no actions can be planned and no expectations can be formed.
It is easy to believe that adding up everyone's expectations is sufficient to extend this to society and assume the same, but it would be wrong. The assumptions and unknowns that individuals face within a society are of an entirely different order than the assumptions and unknowns a society must face. Each of us is a small enough part of the whole that our actions and expectations do not much effect that of the whole, but the whole of us is broadly affected by the whole of our actions and expectations. As individuals we can estimate savings rates, inflation rates, interest rates, discount rates, return rates, and tax rates, but a society cannot because their actions and expectations are not independent of one another.
Finance is much more complex at heart, and a dollar in time is as illusory as our ability to predict the distant future. A society cannot assume a rate of return, they must produce it. A dollar in time will be worth whatever society will make it worth. Assets require considerable reinvestment over time to maintain their usefulness. Few have lives even approaching that of individuals, and changes in circumstance and technology can make them obsolete even before then. We inherit the natural environment, our knowledge and technology, our institutions and society, and the state of world as it exists, but remarkably little else over a lifetime. We have done well if we leave it improved.
We can acquire assets in other societies, but this is dependent on someone having the means and desire to acquire them in the future and not every society can have a positive net balance with every other society so these may be a poor store of value, but everything may be a poor store of value.
Money and time are considerations for work, debt, savings, transfers, and retirement. For an individual, societal rank is often more important than absolute level as it will determine their call on societal resources, and this is what their savings provides. For societies, absolute level is usually more important since others are more distant and this will determine their call on world resources and their standard of living. Most of what we consume must be produced shortly before, from perishable food, worn clothing, household maintenance, depreciating autos and equipment, and deteriorating shelter. Shelter and furnishings are among our longest lived personal assets and both require regular maintenance and upkeep. Little can be stockpiled and stored in any sizable amount for any considerable time. Our main choice, if it is a choice, is whether or when we transition from work to retirement. Even that is transfer in part since remaining in the workforce will lower the real wages of other workers. Dependents always live on the efforts of the independent. How well they live is largely dependent on the productivity and numbers of those providing for them. Debt, savings, and transfers are largely how we divide this output and all are burdens on producers, but production limits what can be divided. The lower the transfers the higher debt and savings and asset prices, and the higher the transfers the lower the debt and savings and asset prices. People retire on the economy they create and live off its product. Society may prosper or suffer and this is the greatest threat to work and retirement, not some numerical return that results.