By John Dodge

CHICAGO (CBS) — Buying a growler of beer is a popular way to enjoy limited edition craft beer offerings or to share a brew with others.

Properly filled, an unopened growler can keep the beer fresh for about a month, some beer experts say, although the time can vary. Others say it might last for a week or two.

However, once it is opened, drinkers may have just 36 hours to finish the beer (a growler typically is 64 ounces) before it goes flat, according to Dogfish Head Quality Control Manager Rebecca Newman.

That can be a deal-breaker for folks who worry their investment would spoil before they could drink it all.

So, these great guys in Portland have designed the uKeg for beer lovers who want to make, say, a limited-edition IPA last longer.

GrowlerWerks’ mission is to make a growler that makes the option of buying draft craft beer more attractive. The company’s developers say the uKeg won’t let air into the beer, maintains proper carbonation and keeps the beer cold.

Here is a graphic showing how the uKeg works:

One CO2 cartridge keeps one uKeg growler full of beer fresh for up to 4 weeks. The cartridges are available online or at kitchen stores for about 50 cents, according to GrowlerWerks fund-raising campaign on KickStarter.

The uKeg will also fit in a refrigerator. It is smartly designed with stainless steel container and brass-colored tap. It’s also much more durable than a glass container.

The project has already proven to be hugely popular. The company has raised nearly $435,000, well above its fund-raising goal.

While the early-bird discount is no longer available, Kickstarter backers can secure a 64 ounce uKeg for $99. The growlers won’t be ready until spring, 2015, but the company will ship a certificate in time for holiday gift-giving.

GrowlerWerks also will offer a 128 ounce version for $129. For $149, the company with laser engrave personalized artwork on the smaller model.