Re: deprecation, I deployed a personal project 7 years ago to AppEngine, and it has run continuously since then, costing me a few cents each month above what the free tier provides. Since then I've redeployed a few times with little bugfixes or features, and all the infrastructure changes together have required a few lines to be removed from config files, and that's it. It still runs exactly as designed, 7 years later. By far one of the best effort/reward ratios I've had on any platform. No OS upgrades, no package version conflicts, no downtime (that I've noticed), just deploy and forget.

That said, I'm not sure I'd use it for anything that might scale heavily with datastore writes. They get expensive very quickly if you can't cache and group the writes.