I am surprised I am asking myself this question. It should be irrelevant in the perfect world. But with TS3, heavy consequences for the ignorant. I remember way back in the past it was imperative to do one of these first or else things will go terribly wrong. And I fail to find any info supporting that now. So ...

Update Base game to latest patch first? Or install all EPs first? Or at this day and age, it does not matter anymore?

I do have reference from:
http://www.carls-sims-3-guide.com/t...nstallorder.php

But I am not sure how old this is.

IIRC, when you install an expansion, the game will ask you to patch the game, so I don't think it really matters.

When I reinstalled everything (except ITTF) not terribly long ago, I installed the base game, patched up to the patch level I wanted, and then installed all the EPs and that worked fine. If you don't, and just let it patch with each EP, it will only do it incrementally so you'll have to patch with each EP rather than it just saying "TS3 is up to date" and continuing. Either way should work, just one ends up being faster.

Sorry to not include the information that I am installing from Origin client instead of traditional DVDs like when TS3 first came out. Hmmm, come to think of it, I went through DVD installation, Steam (which totally dictates how the game/patch installs), and now Origin client. To clarify, I can click "Download" per icon of each EP as a way of installing. Thus I can decide to "install" all EP before even starting the game and patch.

Install base, patch using MTSPD, install all packs, patch with MTSPD again. This covers everything.

The official instructions buried somewhere in the EA help section suggest to install the base game first, then patch and then install the rest. This was different up until Generations when you had to patch each EP separately, but with TS3W.exe now as the universal exe, it doesn't really matter anymore, I guess, so patching first at least is the "official" way.

The method still applies - either one : patch-first, or packs-first - it does not matter. Of course, only the installation source would differ as that depends on the delivery medium - DVD, Origin, or Steam. And everyone who uses any tools should know where that tool stores its files. If not, go and investigate!
But the packs-first method is more prone to errors because you're "touching" the game files more often (patch included in the DVDs are also sometime not current) . If you have the Digital versions, there's no choice though, patch-first always.

Game Help:TS3 EADM Issues^wiki
Incidentally, the paths are also already documented for Origin, so you know where to look if you want to backup the digital installers. It should be similar on Steam, but as I don't have any games on that Client, I can't capture any screenshots or document it.

I'm also always baffled why people can search on other sites but not on the Wiki. The steps are documented and have been for some time and linked to, at the bottom of the Game Help:TS3 Uninstall^wiki page. I suppose I should tweak it to reflect that we now have Superpatchers and can skip some of those steps. And also the fact that the Alternative is now more suited to be termed Standard, and vice versa. So, if nothing else, it is good that, this page is on my radar, again. (unless someone wants to do it before I can get to it, it is a Wiki, after all.)

I want to report back...

I came back to TS3 by buying from Steam Christmas sale last year (12/2013). Steam does all the patching. But after confirming with Origin virtual rep (online live chat) I deleted TS3 on Steam and installed TS3 from Origin client (a way to get back all my EP from 2009).

From Origin client, naturally I installed Basegame first. Game launcher asked me to patch, I went ahead (with some prayers). I then tried my best to install EP in order. Surprisingly ... beside the Basegame, no EP asked me to patch. I haven't put everything (CC, saves) back into the game yet, but so far TS3 runs smoothly. I guess this time I turn out to have worried too much.

Thanks for all the responses. @tizerist, I still don't know what MTSPD is (please remind me, I am bad with abbreviation). @ellacharmed, there are so many information on internet, the hard part is to sort through and identify which one is irrelevant. EADM Issues ... I wouldn't know what EADM means. And TS3 Uninstall ... I am trying to install the game here. But most of the thing I am very skeptical of is the date of the instructions. TS3 EADM's last update is somewhere in 2011, for an example. People are so helpful to write great help pages, but we gamers can't seem to "trust" content written years ago to such game like TS3. Half of the CC on MTS don't work with 1.67 (a wild speculation). This is why I would hit up and get some fresh responses from fellow gamers. It's more assuring.

Once again, I am happy the game is running smoothly (thus far) and I don't have to pay $$$ to re-purchase the EP I bought 3 years ago on DVD.

Mod The Sims Patch Downloader, the simplest way to patch.

EADM: EA Download Manager... Now also referring to online purchasing sites (Origin and Steam) who are authorized to provide Sims content for download, but was originally an actual program installed with the game with EA's world-renowned efficiency and fortunately discontinued a few years ago. (Ok, I'm one of the ones who had no end of trouble with it.)

(And it is more likely that anything on the site that is current for 1.63 is current for 1.67... Apparently 1.66 and 1.67 were both jokes disguised as patches. )

Pfft! You guys clearly didn't click on that EADM link! Tsk tsk tsk.

Since this appears to be tomomi's issue and not a general Gameplay discussion topic, I'll go ahead and lock it since you have already gotten your answers and Technical Help queries goes into well "Help". Before it degenerates into "Help! I'm having this same issue!" kinda posts.