How old is considered fully cooked?

In the midst of a recent discussion on conformity, religion, clothing and parenting (I know, quite a combination), I was told by someone significantly older than me that my idealism, my lack of conformity and my overall bullish nature will give way to pragmatism, conservatism and conventionality as I get older. I'm in my fourth decade of life.

How old do I have to be before I can officially be declared fully baked?

An idealist for life?

A perpetual non-conformist?

A frequent challenger of tradition and norms?

In truth, I like to think of myself as a logical realist, but regardless of the nomenclature, after almost four decades on this planet, will I really change so much in the next two or three decades that my outlook on life will be entirely different?

Simply put, how old do I need to be before people will stop warning me that I will see things very differently when I get older?

The most distressing part of these conversations is the realization that by the time I reach the age of my older friends and am finally in a position to say, “I told you so,” most of my older friends will likely be dead.