The key is to be qualified for a job, but not walk into the job a total master of all the tech being used. When I was hunting for a mobile job, I was hunting mobile jobs that didn't use objc because I knew it fairly well, but stuff like phonegap. This allowed me to code entirely in javascript and as a result, I got mobile experience which I wanted + JS experience, tech I haven't really used before. Keeps the job exciting, basically getting paid to learn.