Leaves can be placed indoors or outdoors. Below are some tips to make sure they last.

Transit

Protect the edges and tips of the leaves in transit, using bubble wrap, air pouches, of best of all, space! Keep the leaf away from anything it might bump into during transit

Metal loop

Leaves have a loop embedded in the back so the leaf can be hung on a wall/fence/tree. For smaller leaves, this loop is made using garden wire which can be manipulated by hand. For larger leaves however, a stronger gauge galvanized metal is used. If you need to make changed to this loop, use two pliers/wrenches. One can be used to holdand support the metal close to the base of the leaf, while the other can be used to bend the metal loop into another shape. If you try to bend this loop without supporting the wire where it exits the leaf, you risk putting a lot of strain on the concrete

Winter

I recommend all outdoor leaves are taken inside during the winter. This is especially important if the leaf is placed in a horizontal position where it may collect snow or ice.
(Anecdotally, I do have leaves that are hung on a tree or fence above the snow line which I leave outside with no problems.)

Cleaning

Leaves that are placed indoors can be dusted or rinsed off. Given the rough surface of most leaves, I recommend using a duster that won't leave fibers on the concrete.
For leaves that are placed outdoors, I recommend rinsing them off very regularly (each time you water plants) to avoid dirt/sand/grime from acumulating in the veins of the leaves. This grime is often rough and if allowed to accumulate, it will start "sanding" the outer coatings of the leaf

Protection

Many leaves have a protective coating using a concrete sealer, which helps protect the leaf from fading. Over time this coating may wear, and it can be reapplied according to manufacturing instructions. You can find concrete sealers at the hardware store. If you choose to apply such a sealer, please take all recommended precautions to protect your safety.