You have one of two choices, either reduce the demand for astronomers, or reduce the supply. Currently, with 6500 astronomers in this country, we are in an oversupply situation for astronomers. The result is that we now have a near collapse in the astronomer job market with very few permanent positions for astronomers, and lots of temporary 1-2 year 'post-doc' and 'contractor' positions available. If it is desired that every PhD astronomer should have a fair shot at a permanent, life-long position, we currently have about twice as many astronomers in the system, which makes that goal impossible. When permanent positions come up each month on the job market, you get hundreds of applicants for each position. Many of those are just 'shopping around' but others are serious applications.
I think that re-instating manditory retirement at 65 is the first necessary step. Even though I am 43 years old, I see virtually no turn-over in tenure-track positions due to retirement as older astronomers decide to work a few more years. When I got my PhD, I was expecting that in the 1990's there would be an escalating increase of retirements, but instead these have not materialized, and my big worry is that when/if they do begin, universities might decide to terminate the position to save money.
I believe that last year there were over 120 PhDs in astronomy awarded. When I got mine in 1982, there were only 95 awarded that year. It has now become popular to advocate that astronomers practice 'birth control' in granting new PhDs. If no new positions in astronomy are going to open as the Nation slides into the final decade of downsizing to balance the budget, I can see the logic in such a call. Given the steadily decreasing quality of astronomy jobs over the last decade, I think that the influx of talent has been a boon to the progress of astronomy, by NASA, and the research made by those astronomers with permanent positions. However, it has trashed the lives of hundreds of astronomers who will never be able to hope for anything more secure than a 2-year post doc the rest of their lives.
Given that universities will still let an unlimited number of graduate students get a PhD in astronomy, we will not see a decline in the PhD production rate in the near future. The only solution that leads to a quality lifestyle is for the demand for astronomers to increase. This will happen if NASA and the NSF support an expansion of research directed at the data obtained from space missions ( the so-called MO and DA support). From what I can tell of the budget forecasts I have seen lately, I don't see this happening anytime soon to increase the 'demand-side' of the equation.
The bottom line is that I have no solution, given that the demand for astronomers is slated to remain fixed and even declining, and that there seems to be no decrease in the supply of new PhD astronomers. This nation cannot promise new astronomers a stable career because for even the current 'standard of living' for astronomers, the maximum carrying capacity of our nations' $1.6 trillion annual budget, you can only support 6500 astronomers. Next year, there will be an additional 130 added to this number!