By Jove, you're right. "Lasts" is used only in the third-person singular form of the verb. Admittedly, it was only in passing that I stumbled on the title AS a native speaker--maybe I just don't believe "beer's it" so I reassigned bacteria--until I read your comment. Reconstructed with a suitable pronoun, the problem is clear: "They...lasts" is wrong, vs. "They...last", which is correct.
Reference
OT digression follows.
Seeing that someone else posted before I got around to replying, you already had your answer, but I kept at it because their* comment makes me think of an even different approach: As a native speaker I wouldn't necessarily read as carefully as a non-native, who's learned the semantics of the language from a different tack. I discovered this when I took foreign-language classes and attempted to deconstruct friend's sentences in those languages; they looked at me both as if I were insane (who cares about this "accusative" vs. "nominative" stuff? It either sounds right to us or it doesn't!). My friends were arguing for "just talk/write and we'll refine", which was an excellent point: the classes to which I'd been exposed taught me an "unnatural" analytical precision, pegging me as a non-native speaker. Native speakers and writers look at word forms (and by that, I mean shapes, not usages), while non-natives tend to take apart what others take as a whole (BAD SHAPES IS ONE REASON WHY ALL CAPS IS ANNOYING: IT FORCES US TO READ LETTERS AND NOT WORDS -- note the clumsy start you should have here as you switch to reading a regular sentence). Unfortunately, I see accepting these grammatical nuances as necessary for integration--and many of them are learned (for example: "known since eight years" is a dead giveaway for foreigners, vs. "known for eight years"). You noticed the object confusion perhaps because you're paying more attention to structure, but I didn't because I'm quickly reading the shape of the sentence. Without your interjection, I would have accepted the title as-is and thought nothing more of it.
Following, I both support and disagree with Anonymous Coward. While I can easily find assertions that the causal sense of "since" is almost as common as the temporal (so a moot point), I agree in the sense that "because" more often defines a causal relationship. The question "Why can you only speculate?" is what leads: "Because I am not a native speaker", while the strict sense of "since" leans towards time: "Since the 1990's...", "It's been 3 months since...", etc. However, I flatly disagree when it comes down to what everyone uses. I hear/use "since" (even: "as") in place of "because" all the time...and
this dictionary (and several of its notes) agrees.
* Note: My singular use of "they" is disputed, but after reading an excellent writeup I tend to choose that over the haughty "one", the clumsy "his or her", or indirections like "a person".