David's experience sounds logical, but mine has been the same as the OP's, no matter how cold and how long the rain lasts. The rainpants just don't get used.
When I was younger, it was a long WPB jacket, patagonia baggies and short WPB gaitors to keep water form running down into the footwear. This worked fine for extended cold treks in the rain as often occurs in the NE US. If I got cold, some fleece under the rain jacket and cap worked better than pants, and I was more comfortable because heat and water vapor could quickly dissipate.
Now I generate much less heat, so find it helplful to wear a light softshell pant in extended cold rain while hiking, and in many other situations as well. Now it is the baggies that stay in the pack. The DWR on the softshell erodes a bit after a while, but can't believe how fast the softshell dries out from the body heat while hiking, and never gets sopping wet. And it is extremely comfortable.
Haven't ever found a use for rain pants, so out they went. But I understand the Pacific NW gives a new definition to wet, so maybe they are useful there.