The only reason to replace them is my concern that they are just old and might start falling apart in the middle of no where. I was just looking at Harris Cycles and my 126mm frame will support a 7 spd freewheel of something like 12-32 which was another reason for considering an upgrade for loaded touring, that I simply didn't have the gearing. Granny is 28t and freewheel topped out at 28t. I almost have that on my road bike (physical therapy version).
I have time so I'll keep on researching this. Thanks for your help and thoughts.