(CNN) -- Technology is not like wine.
Electronics almost never gain value after they've been sitting around for a while, but some stand the test of time better than others.
As Apple is reportedly readying a third-generation iPad to be unveiled in the next month or so, owners of previous versions of the tablet may be contemplating a way to unload them for cash. Fortunate for them, the iPad can be resold for about half its original price a year or more after it hit the market, according to data from two popular online researchers that was compiled for CNN.
On the other hand, Amazon.com's Kindle devices, which analysts say pose the greatest threat to Apple's dominance in tablets, have not been as sought after in the secondary market.
The various Kindle e-readers generally are worth between 25% and 33% of their original price a year after their releases, according to data from electronics reseller Gazelle.
After a year, the Kindle's value can sink even faster. The Kindle 3, a 2½-year-old product still being sold by Amazon for $139 under the name Kindle Keyboard, can be worth far less. On the secondary market, the Kindle Keyboard is worth about $16, according to data from Decide, a firm that researches electronics commerce.
Amazon didn't respond to a request for comment on these statistics. Likewise, an Apple spokeswoman declined to comment.
One might assume that because the iPad is more expensive than even the top-of-the-line Kindle ($499 to the Kindle Fire's $199) that Apple's tablet is likely to depreciate more quickly. But Kindles, on average, depreciate 22% faster than iPads, Gazelle executive Anthony Scarsella wrote in an e-mail.
How the Kindle Fire, Amazon's first touch-screen tablet computer, will fare in the resale market is unclear. It is only 4 months old.
But Amazon is expected to continue with its strategy of regularly releasing improved models at drastically reduced prices. Apple typically releases improved models at the same price as their predecessors for phones, tablets, computers and iPods, which can help previous versions retain more of their value over time.
"Kindle's frequent price drops combined with multiple models now available heavily contribute to its reduced Gazelle value," Scarsella wrote. "Similar to what you see in Andriod phones (lots of model updates and frequent price drop) compared to iPhone (few models, stable pricing), the iPhone holds about 60% of its value one year after launch while even the best Androids only hold about 40%."
Indeed, another firm called Priceonomics reported similar resale-value discrepancies for the iPhone and ones that use the rival Android software from Google.
However, some types of Apple gadgets are less wise investments for gear heads who like to resell their wares in exchange for newer models. Paying an extra $100 or $200 for double or triple the storage space will never result in a decent payoff later, a Decide spokesman said in a statement.
Of course, pouring your money into gadgets may not be exactly the best financial strategy anyway.