Question about Origin Access and Sims Packs

I think, and I'll admit I don't know for certain but it would be really bad business practice on EA's part to not work like this, that any pack you buy with an Access discount you'll still be able to use fully. Now, things like the Deluxe add on - if you didn't buy the deluxe version initially - I'd expect to deactivate as if you'd uninstalled the pack.

My free trial just ended so here's my experience. Any game you purchase you can still use after access ends so take advantage of the 10% off while you can! If you upgraded your game to deluxe for free you cannot access that content after. The game will be grayed out but don't worry, to open your game click on the game and the gear button to open the setting, there should be an option to revert to the purchased copy which will remove the deluxe content and allow you to play normally. It will not remove anything you purchased, just the free content from access.

Good guess on how it works @DaWaterRat, and @Felicity1169 explained it perfectly! The 10% discount is applied to purchases while you are an Origin Access member. If your membership expires, the purchases you made will still be in your Origin Game Library and you can keep playing as usual. Basically, it works as if you purchased a game during sales. :)
However, games from The Vault that you added to your Game Library for free during your Origin Access membership (this includes Deluxe upgrades or packs) won't be accessible anymore if your membership expires.