C++ const keyword - use liberally?

In the following C++ functions:

void MyFunction(int age, House &purchased_house)
{
    ...
}


void MyFunction(const int age, House &purchased_house)
{
    ...
}

Which is better?

In both, 'age' is passed by value. I am wondering if the 'const' keyword is necessary: It seems redundant to me, but also helpful (as an extra indication the variable will not be changing).

Does anyone have any opinion as to which (if any) of the above are better?