And I'm free to stop subscribing if the service gets worse (or doesn't get better as fast as I'd like).
If you have the data locally, you can always migrate it - whether manually, through the software that made it (e.g. if the app isn't supporting your new OS, then run it in a VM with an older OS to export to a more forward-compatible format), or through third-party converters. If enough people are in this position, someone will write a solution.
If your data resides in the cloud, however, it's up to the vendor whether or not you'll be able to access it or export it, and how much of it. If they're just sunsetting the product, you probably, maybe, will be able to get some data back (which is almost definitely in some unknown ad-hoc format, quite likely a database dump in form of JSON, so you'll need a converter anyway). If they terminate your account because of $random reason, you won't even have a chance.
Or, to borrow a cliché, "not your files, not your data".
Assuming those exist.
Notice, getting stuff out of Facebook - or Twitter or similar walled-gardens - is double quandary. How you do scan/scrape/whatever the data and how do you avoid being banned for doing so. This given the formats/apis etc constantly and the degree of abusive platform protection also changing (we've seen Twitter's upheavals, imagine a similar abusive dictator buying Facebook and see how much he can squeeze).
And I'm sure someone will "you shoulda know about Facebook but my subscription sure ain't gonna trap me, no". Okay then...
Once the company has lock-in, you have no control over their pricing. The reason a company offers a good deal on a subscription is to get enough customers for it to be worthwhile to start soaking those same customers for whatever they are willing to pay - or imposing things to get more money or etc.
You can see this play out with MS Windows, Twitter and so-forth.
It gives me faith that they can actually sustain their business and pay their employees to maintain and improve the service over time.
Edit: It's amazing to me that someone thinks they can give a company money and expect it to be spent on what they want. The company always to prefers to pocket your dollars as profit. If you send them a check or something, that's what they'll do.