Are your favorite stars rocking naturally long locks? Chances are, they're faking it. (With hair extensions, of course!)

Celebrity stylists and hair extension experts Laurent Dufourg of Privé Salon and Patrick Melville of the Patrick Melville Salon and Spa are dishing who has extra help in the hair department, and sharing their tips on what it takes to get the look.

Who Has 'Em?
When asked which stars have hair extensions, "They pretty much all do," says Patrick Melville. "If they don't have them right now, they have used them at one point in time -- celebs like Britney Spears and Fergie, for example."

How Long Do They Last?
"Individual extensions generally last 3 1/2 to 4 months depending on care. At about the two month mark a "tidy cut" would be required. This is a tightening, clean up of the extensions," explains Laurent DuFourg.

Damage Control
While many women worry about extensions causing damage to hair, trusting a seasoned professional can minimize the risk. "If the extensions are placed in the hair correctly, there should be no damage at all," says Melville. However, with extension types that are bonded to your hair, there is a greater chance of damage than with pieces that are simply clipped or sewn in.

The "Natural" Look
"To get totally undetectable extensions, go to your salon and have your colorist color them for a perfect match to your hair," suggests Melville. "And of course, if you want it to look natural, use only extensions made with real hair." While human hair extensions are pricier than synthetic hair, they have many advantages -- aside from looking realistic, you can also cut, color, and style them, whereas nylon strands would burn or break.

Fallout Shelter
According to Dufourg, extensions do loosen and fall out, "especially if you have oily hair." But how you handle your hair also plays a role in how long they last. "If you are rough with them and over-style then they won't last as long as with normal wear and tear," he says. So limit how often you style your hair, and be gentle with it at all times.

Wash This Way
"Great shampoo is essential to making the extensions last longer," says Dufourg. "Using shampoos that are sulfate-free is key." Sulfates, the foaming agents in most shampoos, can have a stripping effect on hair's moisture and color, and can also affect the bonds of extensions.

Condition Carefully
"After shampooing, use a sulfate-free conditioner. Lightly comb through extensions with gentle tension to get out all the knots and tangles," Dufour suggests. "Rinse out the conditioner well, and use a LIGHT leave-in conditioner. One thing extensions lack are moisture and shine, so a lightweight leave-in conditioner will add a protector barrier shielding your extensions from harsh elements, weather and free radicals."

Get Styled
"When it comes to styling, make sure you dry your hair properly," cautions Dufourg. "Use a blow-dryer and your fingers to dry hair about 80 percent, then use a round brush after to finish. Extensions tend to hold a lot more water [than your own hair] so make sure to get them as dry as possible before picking up the brush. If you're using styling tools, remember that extensions don't need a high heat, and use a ceramic flat iron or curling iron -- they're less damaging than mental."

Click here to see which summer hair trend has celebrities bursting at the seams.

Reporting by Marissa Gold