By Louis Ramirez, dealnews Senior Feature Writer The iPhone 5 is coming, and for current iPhone owners that means one thing — it's time to start shopping around your now-dated handset. However, you may want to carefully consider your options before selling, as one popular trade-in site is extending its price-lock guarantee in anticipation of the iPhone 5. Typically with many trade-in sites, the longer you wait to sell your item, the less money you'll get for it. So as we've noted before, an early sell guarantees the most cash for your device. However, this week, trade-in site Gazelle announced that it's giving iPhone owners the opportunity to register to sell their iPhone today and receive an August quote, and then lock-in that rate until October 1. This way, customers can take advantage of the earlier — and likely higher — trade-in value, but keep their iPhone until after the new one supposedly debuts on September 12 and shipped on September 28. This is special for the Apple announcement, as Gazelle usually gives users a quote that's valid for only 30 days. For the iPhone 4S, that period has been extended to over a month. And even then, customers aren't obligated to sell their iPhone to Gazelle, and can choose to keep their phone instead. How Much Can You Get From a Trade-In? So how much green can you expect from Gazelle? As of August 22, a "flawless condition" iPhone 4S 16GB Smartphone for Verizon will earn you $280, while a "good condition" iPhone 4S 16GB Smartphone for Verizon will get you $260. By comparison, NextWorth offers $274 for the same flawless phone, and that value is only valid for 21 days. Meanwhile, shipping it to Glyde will net you significantly more, at about $355. But, you must part with the handset now in order to secure that trade-in price. Amazon Trade-In takes the cake, however, by offering a healthier $410 Amazon credit for the same "like-new" 16GB iPhone 4S for Verizon, and a $348.50 Amazon credit for a "good condition" version of the same iPhone. Amazon's rate, however, is not guaranteed through October and payment is via an Amazon credit, rather than cash. (Click here for a look at all of Amazon's trade-in options.) Gazelle for Some, Amazon for Others If you know you're going to upgrade your iPhone and you frequently shop at Amazon (who can't find something they need at Amazon?), then your best bet in terms of optimal value is to sell now via Amazon's trade-in program. However, you'll need to fork your phone over and wait eagerly for Apple to unleash the iPhone 5. Conversely, if you're still on the fence, or you can't stand to go over a month without your trusty phone at your side, then Gazelle's offer is an enticing option. It doesn't offer the highest return, but it's the only one currently extending its price-lock guarantee. To take advantage of the offer, simply head to the site, look for the iPhone model you currently own, and secure your quote. You can hold onto your rate — and your iPhone — until October 1. Related dealnews Features: The iPhone 4S Will Drop in Price at the iPhone 5's Debut, But by How Much? Apple Stores Will Match the Latest iPhone 4S Price Cuts, But Should You Buy? Prepaid Cell Phone Plans Save Money But Remain Unpopular with Consumers An avid gadget lover, Louis Ramirez has covered technology for Gizmodo, CNET, Laptop, and various other publications. Follow him on Twitter at @LouisRamirez Follow @dealnews for the latest roundups, price trend info, and stories. You can also sign up for an email alert for all dealnews features.