Like someone said, if you are subscribed for instant email notification, it only sends one email for the first new post since you last logged into the site (or if you remain logged in, the last time you opened the page whether you viewed anything or not). For any subsequent new posts, beyond the first one you were notified about, no email is sent -- it expects that you will log in to see the post contained in the email, and view all new posts at once -- otherwise it would fill your inbox with alerts. Once you log into the site again, whether you visit/read this thread or not, it marks all threads on the forum as viewed when you leave the page, and will again notify you of the first new post after you've left the page.
There are two ways to think you are not getting notifications properly. First, if you get the email and don't visit the site. Until you visit the site, you will never receive another notification no matter how many new posts happen after the one it alerted you about. Second, you get the email, but don't follow the link in it straight to this thread. You instead log into garage journal and browse other threads, and forget about this one. When you leave, you'll get a new alert for the first post that happened after you've left, but you'll have missed/think you read/forgot about those posts that happened between alerts (unless you scroll up). There is a third thing where if you are currently responding to a post (like I am now) or have the browser open on the page for a while either viewing the thread or dropping a deuce, or even just browsing the overall site for a long time, it can get a little screwed up on whether or not you've left and need a notification, so you may need to scroll up a post or two on each visit to make sure it properly brings you to the newest thread. And you can bet that there are at least a few posts a day. If you go more than a few hours without a notification, for whatever reason, drop on by and double check and "reset" the notifications because something probably happened.
On the topic of sites that put all deals in threads in a forum, slickdeals is another example of a site that puts each deal into a thread. Hell, it seems like half the deals posted here were on slickdeals first. IMO their site is a nightmare to deal with and keep up with (thank God for the iSlick Pro app). Partially because they get so many deals, but also I find it hard to keep track of everything when old threads are at the top because of new comments, and new deals with no comments get pushed down, are on the next page, etc. This is especially especially difficult if you visit the page, and don't have the time to view every single thread in a visit. Then you can forget about it keeping track of what you have and have not read, and you wind up reading and rereading everything to make sure you're up to date. What a nightmare. IMO, we should keep this thread singular as long as we can (as long as we have few enough deals and chit chat that it is not too unreasonable to view this way). If a lot of guys can barely manage alerts on this thread, it seems that dealing with alerts for a full forum, dealing with finding the deals you want, and keeping track of what you have and have not read would be even harder with a sub forum?