Miley Cyrus and Liam Hemsworth are head over heels in love. So much so that they surprised both fans and family alike with their sudden engagement announcement last May 31.

While some die-hard Miley fans are screaming their lungs out of excitement, a few critics are weighing in on the engagement. How long will they last?

Former Disney star, Miley Cyrus, is no longer a kid not because of the risqué clothing. Instead, Miley proves to be growing up real fast because of mature decisions she's been throwing herself into.

The engagement with the longtime beau, Liam Hemsworth, should of course be a joyful announcement for fans. Yet, aren't Miley and Liam too young to be married and living the "married" life?

Billy Ray Cyrus has already given the couple his blessing. In a separate interview, Tish Cyrus claims that Liam Hemsworth is the "love of Miley Cyrus' life". Still, it does not justify the "sudden" decision to get hitched.  Liam Hemsworth, on the other hand, says he sees nothing wrong with getting married at a young age. In fact, the Australian actor had been inspired for a young engagement because of his parents.

"They have a fantastic relationship and he idolizes them (his parents)," shared a source to The Telegraph.

"The thing Liam and Miley have in common is that both have very strong parental role models. They are madly in love, why wouldn't they want to get engaged and move in together?," continued the source.

Well, sure they may be madly in love for now. Yet, take a look at all the other celebrity couples who wed at an early age. One would be Drew Barrymore who married Jeremy Thomas at the age of 19. The two split the same year. Another couple would be LeAnn Rimes and Deam Sheremet, LeAnn was also 19 then. The two split and now LeAnn is married to Eddie Cibrian.

"They may be lovely, wonderful people with two brains that haven't finished developing yet," shared Dr. Toni Thomas Luskin for E! Online. "Their brain development is going to be very different in a few years than it is now.

A 19 and 22-year-old are immature in the sense they still can't quite be as selfless as they recognize they will need to be a few years later. Would we choose the same life partner at age 19 or 22 as we would at age 30?," continued Thomas.

With Miley and Liam's history of an on-off and on again relationship, will their marriage really last that long? If the marriage does last then for how long exactly?

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