If current trends[1] continue, it will take about 15-25 years for solar energy to become cheaper than fossil fuels, which seems like a reasonable length of time for a trend to continue.

To get the installation cost down from an estimated $1.40 in 2020 to $0.10 and $0.01 with the same trend would take 30-50 and 60-100 years, respectively. 70-110 years is definitely further in the future than I am comfortable peering; 40-60, also a little shaky.

But given current trends, it looks like 2050-2070 is roughly what you need to shoot for to live to see $0.10 / Watt solar energy. If you were born in America after 1976, I'd aim for 2076; it'd be nice to see the Tricentennial.

[1] http://www.bloomberg.com/news/2011-04-05/solar-energy-costs-...