Build a better mouse trap... curtain rods and brackets have historically been a design quandary (for me, at any rate). Extendable rods have an ugly impractical transition between the two halves. Finials are not pretty - almost without exception. Brackets tend to sag and can have a tough time holding onto or letting go of a rod. And just throwing money at a problem does not assure better options.
My solution is a fairly simple woodworking project that incorporates graceful, beautiful materials: 1 x 3 poplar (or maple) - actual measurement .75" x 2.5" (stocked at The Home Depot, if you must) cut into 4" lengths and pre finished hardwood broom handles cut to length. Tools include a drill with a 1" paddle bit and a 1/8" bit, a hammer and 1 1/4" finish nails, 2" #8 wood screws, wood glue, a tape measure, 120 grit sandpaper, a wire hanger and wire snips. If you have the wherewithal to cut your own blocks safely out of reclaimed wood - fantastic.
Mark a point 1 1/4" from three sides on the face of a wood block. Drill a 1" hole cleanly through the block at the mark. Sand this piece and attach it perpendicularly to the center of a second block with wood glue and finish nails (see above). The rods are not generally long enough to extend across windows over 42" so a center bracket is necessary where the two poles meet. I like to cut them leaving the rounded end of the rod with about a 1 1/2" overhang (NO finial). To keep them in place, mark the pole at the inside of the lefthand and righthand brackets drilling a 1/8" hole through the rod at these points. Install the rods and curtains. Thread a 2" piece of hanger wire through the holes bending each end slightly to keep the wire in place.
I find that attaching the brackets to the wall works well by pre drilling a 1/8" hole center top (angled down) and at the bottom (angled up) through the block - yes, I did it differently in the pic above (I have a brad nail gun, okay?). Attach with standard 2" wood screws. If your drapes are heavy you may need wall anchors.
I like finishing the brackets with linseed oil (prior to mounting). But it can be decoupaged, lacquered...