I don't know why you originally eschewed the web. I've developed on closed platforms in the past: Facebook (when Facebook games like Farmville and Mafia Wars were crazy hot), Silverlight, OpenSocial, Twitter, and now Google Apps Script. My work is always worthless in 2-3 years, and what I "learned" about that platform is useless.
Now when I develop for a platform, my mindset is only if it's temporary, and if I will be okay if this is shut down in a year.