Adjustable, telescoping basic white curtain rods have been the "go-to" product in the window treatment industry for decades. They're relatively inexpensive, easy to hang, plus they quickly adjust to fit your window. With the popularity of thicker, heavier, lined or interlined draperies, you may find that a pre-packaged curtain rod isn't the right choice for your window. You might need to consider a heavy-duty curtain rod instead.
If you're looking to replace an existing rod, there are some tell-tale signs that a pre-packaged rod probably isn't the best choice. Probably the most obvious indication that a heavy duty rod is the way to go is broken carriers on your existing adjustable rod. If the carriers keep snapping and breaking off, then the weight of your drapery is too heavy for a pre-packaged rod. Another indication is resistance to draw. If you find it difficult to open and close the curtain with your cord, then the fabric most likely exceeds the weight that the pulley is designed for and it's time to upgrade.
The fact that heavy duty curtain rods are solid, non-adjustable tracks goes a long way toward providing superior carrying capacity. Plus, most heavy duty rods have wheeled or ball-bearing style carriers that don't break or snap off with frequent use over time. These specially designed carries allow your curtain to effortlessly glide open and closed. Super strong end pulleys are designed for even the heaviest fabric so you won't have to struggle with the cord.
For a one-way left or right draw, the amount of weight a pre-packaged rod can handle drops significantly because the draw end pulley is doing all of the work for the entire span of the rod. That's why you'll only see split draw pre-packaged rods over a certain size. It's always a good idea to consider a heavy duty rod if you need a one-way draw rod larger than eight feet or so. Even if your curtains aren't too heavy.
Depending on the size you need, you might actually save money with a custom made heavy duty rod. Adjustable rods in the 120 plus size are always going to have to ship to your home on a semi-truck instead of regular ground and the freight fee can be three or four times the cost of the rod. If you choose a custom heavy duty rod, it can be manufactured in two sections if you want a split draw and ship regular ground. The net cost will most likely be lower.