Use or Discard By
Use or Discard By
[Megan stands in the middle of the panel, holding two flare guns, one in each hand.] Megan: These emergency flare guns are about to expire. Cueball [off-panel]: I forgot we had those.
[Cueball sitting at a desk, working on a computer.] Megan [off-panel]: This one says "Use or discard by Apr 25 2020." Cueball: Okay...
[Megan holds up one of the flare guns looking at it. She holds the other flare gun by her side.] Megan: But this one just says "Use by" ... Cueball [off-panel]: No.

Many products carry a "Use By", " Expiration date ", "Discard by" or similar date.  The date shows the latest date by which the product has been verified to provide its expected use. For example, a foodstuff will have a "consume by" date, showing the date after which the food may be unsuitable for eating.  For most products, this is a conservative estimate, especially if a product is kept sealed and stored in a cool, dark place. A few products become dangerous to use after that point, some simply become stale and less palatable (as in the case of foods) or lose potency. For most consumer items, there's no immediate imperative to discard a product as soon as it expires; you simply take the risk of a decline in quality or reliability.
One of the issues around expiration dates is that the language used tends to be arbitrary and ambiguous. Some have explicit instructions to the consumer, such as "use by:", others have instructions to the seller, such as "sell by:", still others say things such as "best by:" or "freshest before:". This can make it confusing how important it is to get rid of a given product on that date.
In this comic, two similar emergency flare guns , an item typically used to send out distress flares , have slightly different expiry instructions. One has an instruction to "use by or discard by" a specific date (in this case, three days after the date of publishing).  The other has an instruction to "use by" this date. These two phrases almost certainly have the same intent. There would be no reason to actually fire the flare.  Even the instructions to discard the flare gun really just mean that the manufacturer cannot guarantee that it will work past the printed date, and so do not advise counting on it in an emergency situation.
Despite this implication, Megan seems to take the latter instruction literally, as an order to actually fire the flare gun prior to the expiration date, whether or not it's necessary. It may be taken that she wants the experience of firing a flare, and takes that instruction as an excuse to do so. Cueball immediately objects to this line of reasoning. Firing a flare unnecessarily is generally a bad idea. It could summon emergency responders to a non-emergency situation, diverting emergency resources that may be needed elsewhere.  Even worse, if a flare is fired improperly, or in an unsafe direction, it could cause a fire and/or injuries, ironically creating an emergency situation, rather than signalling one. This was the cause of a serious fire at a Frank Zappa concert in Montreaux in December 1971, which inspired the well known song (and infamous guitar riff) " Smoke on the Water " by Deep Purple .
The title text similarly indicates that Megan intends to follow the same instructions with a can of bear spray .  Since there are no bears present, she will go camping and leave her food out to attract their attention, so that she may use the bear spray to repel bears before it "goes bad".  This would involve approaching bears (close enough to spray them) and irritating them, potentially causing them to attack if the spray is ineffective or misapplied (perhaps it only works if they smell it, but Megan might spray another part of the bear), when it would be much safer to simply discard the bear spray and not get close to bears.
Expiration dates (for food) have also been mentioned in 737: Yogurt , 1109: Refrigerator , and 2178: Expiration Date High Score .
[Megan stands in the middle of the panel, holding two flare guns, one in each hand.] Megan: These emergency flare guns are about to expire. Cueball [off-panel]: I forgot we had those.
[Cueball sitting at a desk, working on a computer.] Megan [off-panel]: This one says "Use or discard by Apr 25 2020." Cueball: Okay...
[Megan holds up one of the flare guns looking at it. She holds the other flare gun by her side.] Megan: But this one just says "Use by" ... Cueball [off-panel]: No.
