No issues with using a pocket replacement window if the frame is sound, even then it may be an easy repair. The trim will typically be wrapped with aluminum trim coil. I would look into the insert replacements were to me over the new construction as you are aware it is less expensive and less intrusive. Since you are in the NE I would look for a Okna, Sunrise or Softlite dealer as opposed to a general contractor as they offer the better window products and they are a factory authorized installer. As far as double hung repair, yeah it can be done but if the windows are original and typical townhouses did not use high end products repair may be good money after bad as 30 years is about the end of the life expectancy of "most" wood windows.

"the wood trim that surrounds the window openings has certainly had a chance to deteriorate with the weather here in the northeast"

That says to me new construction windows because the frames have deteriorated. Also note that most insert replacement windows will have a decrease in the amount of glass from what your original windows had. It may be a negligible difference or it may be significant, depending on the manufacturer and the size of your windows.

Since you said your windows are wood, and you live in a townhome, I would check with your townhome association if they will allow the the vinyl windows of Okna, Sunrise or Softlite suggested above. Some associations are very particular about which types of windows they will allow to ensure that all the townhomes/homes look the same. Some associations are so particular they may even dictate which window brand you must get. So check with them first.

To M Miller. The existing windows are Vinyl. The surrounding trim is wood. And you're right, the HOA is particular.

On the topic of Okna, Sunrise, or Softlite. I spoken to at least half a dozen installers or window contractors in the past week. With the exception of Softlite, no one has ever heard of them around here (and only one person has heard of Softlilte). I don't doubt the testimonials on here as to their quality. But they are hard to find and don't have much of a reputation around here (greater NYC area). Also, even going to their websites there aren't dealers very closeby, which probably explains it.

Westchester County in NYS.

"I bet the wood trim is only chipped paint which isnt “ rot”. Even if it is, its a very simple repair."

There is no way to know that without seeing the frames. The OP said she lives in the New York City area. Given the climate and the 30-year age of the windows, it may well be that the frame is rotted. In addition, on a previous thread, @William Rossman wrote "Repairing a 25 year old builders grade window is like using bubble gum to hold a hair piece on a bald man’s head. It may do the trick for a few minutes." The OP on this thread has 30-year-old windows. @William Rossman, please explain your opposite advice.

The OP said specifically that the HOA is particular, so that does not jibe with your advice that "they are always very easy to deal with". How would you know that better than the OP who lives there?

A little more clarity. I've inspected the window trim. None of them have obvious damage to the trim from the outside so it is possible that what William is saying is true.

But the installer who does only new construction installs insists that in his experience, he has not only found damaged or rotted wood, but he feels that the additional flange on the new construction installs makes for a better seal and a sturdier window with more integrity and durability.

I had another installer here today who does Anderson, Marvin, and Pella and when I asked him for a quote for a new construction install he looked at me like I had two heads on. "Why?" he asked. I told him it's been recommended by several. He pretty much gave me the feeling that they never do new construction installs for replacement windows.

Scratching my head.