No Heat

The Heat in my car does not work properly. Various mechanics noted that my antifreeze is not the typical green color and instead is a rusty brown. When the antifreez was fkushed the heat worked for a few weeks but then slowly it becomes luke warm at best and the rusty color comes back. I have been told that the antifreeze itself has retained its quality and that the rusty color is from a deteriorating heating core. Does it make sense to replace the heater core on a 1998 Honda Accord with 130k and a potential future transmissin issue and is the heater core the most likely problem?

130,000 miles is not much on an Accord. Has the timing belt been changed?

Sounds like the heater core is plugged up, was the coolant changed frequently enough?

Shop around, how much for a replacement?