Most of my clients are, as you mention, skeptical of employees with incredibly long tenures marked by limited accomplishments and static skills. I also can't sp

Most of my clients are, as you mention, skeptical of employees with incredibly long tenures marked by limited accomplishments and static skills. I also can't speak as to the percentage of potential 'age bias incidents' that stem from this type of situation, but attitudes towards employment and loyalty are certainly a factor. Career fluidity has only been a somewhat accepted industry trait for the past 10 or so years. I had clients circa 2005 that wouldn't look at a resume for any candidate that hadn't been at their current job for 7+ years, which eliminated everyone who had taken a chance on a startup during the first dotcom wave. The generation of technologists that started work in the 80s and early 90s likely had pensions and other retirement benefits that made staying at their job an easier decision, and they were likely raised with different feelings towards employer/employee relationships. Flash forward to 15-20 years into their career, and the job market, the definition of marketability, and job search itself changed dramatically. It's easy to point to ageism, but that's not really it, because the ones that joined startups or moved around a bit aren't seeing that same level of stigmatization. If someone is maintaining that PHP4 app at BigCo for 10+ years, I'd think that person would probably need to demonstrate that they've been paying attention to dev trends or they won't get looked at. If you're not getting challenging work at the job, you need to find it somewhere else. I started offering resume and career consulting services to job seekers over a year ago, and a large percentage of my clients are people in this boat who need to reinvent and market themselves to appeal to today's employers. It can be scary to look for jobs today if you haven't looked in 10 years.