So, I decided to do a bit of investigation:

SL Reports:
18-24 year olds account for 15.42% of usage time
25-34 year olds account for 34.76% of usage time
35-44 year olds account for 28.31% of usage time

The census bureau as of 2004 (the latest year I could easily google data for) Reports:
18-24 year old population is 20,971,000
25-34 year old population is 40,032,000
35-44 year old population is 44,108,000

So, accounting for population distribution, the 25-34 year olds spend slightly (~2%) more time in world, per percentage of the US population, than the 18-24 year olds.

There are a couple of caveats to this data, its from 2004 census and its only US, but since the original post tried to draw conclusions based on US child rearing habits of the past couple of decades, I don't feel too bad about using the same basic data. Also, it is usage data, not population data in SL, but I couldn't find data specifying the numbers of users of the various ages in SL.

So, given a bit of better data analysis and the relative similarity of the usage data, I feel that it's specious to conclude that the Millenials basically need things "spoon fed" to them.