You should act quickly to get the top trade-in price before the new Samsung Galaxy S6 and S6 Edge are released. Thinkstock By Cameron Huddleston, Former Online Editor March 11, 2015 There’s nothing like the announcement of a new smartphone model to make the one in your pocket suddenly drop in value. Case in point: After Samsung’s February 2014 announcement of the Galaxy S5 smartphone, prices on older models dropped as much as 5% on the secondary market before the new model was even available to the public, according to electronics trade-in company NextWorth.SEE ALSO: How to Cut Smartphone Costs Now that Samsung has unveiled new Galaxy smartphone models – the S6 and S6 Edge – the Galaxy S5 could start dropping in value on the secondary market soon, says NextWorth Chief Marketing Officer Jeff Trachsel. So if you have a Galaxy S5 and want to upgrade to an S6, the best time to trade in your current phone at a Web site that buys and sells used electronics to get the most value for it is now, he says. The longer you wait, the more likely it is to decline in value. For example, NextWorth’s research shows that Galaxy S4 models dropped 23% in value within two months after the S5 was released to the public. So that means that a Galaxy S5 in good condition that you can sell for about $165, on average, now at trade-in services such as Gazelle, NextWorth and uSell.com would likely sell for about $127 a couple of months after the release of the S6 and S6 Edge sometime in April (assuming it loses value at the same rate). The U.S. release date isn't certain yet, but the Galaxy S6 and S6 Edge are expected to be available worldwide starting on April 10. If you want to maximize the trade-in value of your current smartphone but don't want to be left phoneless for an indefinite period, take advantage of price guarantees offered by NextWorth and Gazelle. Their price quotes are valid for 30 days after they are issued. So you can lock in a trade-in price for your Samsung smartphone now before it drops in value, but still keep your phone until the new Galaxy S6 and S6 Edge are available. Advertisement In the meantime, if you find that the wireless providers and smartphone retailers will let you trade in your older model for a credit toward the purchase of a new phone that’s worth more than the price you were quoted by NextWorth or Gazelle, neither company will require you to follow through with a trade-in if you haven't already shipped your phone to them. It’s worth noting, though, that many retailers only accept select phones, and most won’t accept damaged phones. But trade-in services accept a large variety of smartphones and will even pay for damaged phones (see What to Do With a Damaged Smartphone). Most provide free shipping for trade-ins, but you will have to wait for your phone to be inspected before you receive a payment. If you want cash on the spot for your phone, you can trade it in at one of the more than 1,800 ecoATM kiosks in malls and select retailers nationwide.