I hate characters being frozen in amber forever. I prefer heroes who grow facing new, greater challenges over time. If the essence of what makes a character unique (their core values, for example) remains I'm fine with them evolving because such change mirrors both Human life and the wider natural world. IMO, nothing is worse than a stagnant narrative, but to each their own. I do think with the dawn of more complex plots in other media the day of the continuous loop American comic book character is (thankfully) nearing its well-deserved end. The audiences of today expect more, and so they should.