So, if I understand you correctly, you'd like a 9-to-5 job where you won't be forced into management and be able to keep your valuable skills to yourself while you work on more interesting things after hours?

I think I am currently in that situation. It's not all it's cracked up to be. First off, your time on nights and weekends is not as long or of the same quality as 9 to 5. You don't have the same energy level or focus.

As for the job, no job is immune to change. If you have skills that are valuable to your employer, you'll find that either your employer will overwhelm you with work and/or they'll seek to have your co-workers gain those skills to distribute the workload. This kind of stuff will make you more and more unhappy with your job and this will surprisingly make it harder to work on your side projects outside of work. If you put all your eggs in one basket by anchoring yourself to the Oracle stack, when you go to look for another job (because you're tired of your current job), prospective employers (and especially recruiters) will see mostly Oracle stuff and you'll be pigeonholed into jobs that are similar to your current job.

Don't make perceived stability the central focus of your job search (unless you have others that depend on you financially). Choose jobs that will serve you better with respect to your career goals. That may mean changing jobs more often than you'd like (but not necessarily so), but you'll get to where you want to be sooner.