Installation order of the eps and sps?

[Pam]

So, just to be sure. Lets say, if I have  base game + latest patch + Seasons, I can just simply install Generations and launch the game from the Seasons pack, right?
I do not have to unistall / unpatch / undo anything...
Also, will my saved games work fine with the newly installed EP?

Yes, this is correct.  To be on the safe side, I suggest making a backup of your game before the installation.  I'm also moving this to the Technical Help board.

[Rinkils]

Thanks a lot for the answer.
However, I am still a little bit unsure, whether I will not need to repatch after installing EP that has been released long time before the patch was made. Basic logic tells me so, unfortunately, I was not able to find a clear answer here yet.
Or is the launcher going to check that automatically and prompt me to do something if necessary?

[Twinmum]

Usually, your launcher will install any updates before it installs the next ep/sp.

[Rinkils]

I can say with 100% certainty that it doesn't matter what order the Sims 3 expansions are installed in.  I had the base game, and Ambitions installed before I got WA or any Stuff Packs, and I also installed Late Night before Fast Lane Stuff.  But before I did any of that, I contacted EA customer support and they confirmed that it doesn't matter what order they're installed in, so long as you use the most current expansion installed to run the game.  So even though Late Night will be the last expansion you install, you'll still use Outdoor Living to run the game.

For Sims 1 and 2, it definitely mattered which order you installed them in, but for Sims 3, it doesn't.

I can confirm it doesn´t matter, too. What I did just today:
1. I only had a base game (1.50 version, installed from a CD as a 1.46 version, released in 2012) + seasons (released 2012), very few store content, no CC, no mods.
2. I patched it via launcher up to 1.57 version.
3. I installed Ambitions from a CD (released in 2010).
4. I installed Generations from a CD (released in 2011).
Of course, between each two consequent steps I was making the required backups, I even backed up the core game files both before and after the patch.
Only thing that the launcher required me to do after installing Generations, was to update my store content, which I did.
Then I started a new game and tested it pretty thoroughly. And it just works totally smoothly and flawlessly.
I tested pretty much everything. There are no errors, no crashing, not even after build mode, not in CAS, not anywhere. All the content, all the EP-specific features, everything is there, it is not conficting with the previosly installed Seasons at the least. I tried to bother the game as much as I could - not a single freeze.
So not only it seems to not matter in which order you install EPs, it even might not be essential to apply incremental patches after each installation, as far as your game is up to date as such.
In case I found some error, I could still digress to the official EA cumulative superpatcher, and I believe it would be fine.
However, if one can choose, it is probably safer to install everything in the right order, and of course, backup everything and test everything after each installation.