Aside from the fact that it's fun to buy the latest thing, how do you really decide when your wheels must be replaced? I have old 26" wheels with low mileage, Suntour XC Sport hubs, straight gauge ss spokes, 4x, no quick release, and 5 speed hub. Aside from maybe replacing the bearings and the inconvience of only a 5 speed freewheel, what criteria should I use when deciding to replace these wheels?
Thanks

Why replace them if they still are servicable and work for you? You could always buy a spare set of wheels in case you have to repair the original set, but then you will be trying to find a 5 spd set up etc to keep on the spare unless you just swap over the cassette while the original is being repaired.

It's kind of up to you. I had a spoke break a couple of days ago after approx. 1800+ miles/three months on my "oem" rear wheel (Ritchey hub/Alex rim). When I started researching about broken spokes I came to the decision that there may be more of this in the future so I went and bought two wheelsets/cassettes to "replace" the originals that came on my Fuji. While I am sure that others will say this is wasteful, I say it gives me peace of mind knowing that I won't be down for repair anytime soon. Once I get the original repaired it will serve as my exclusive rear wheel to use on my trainer.

BTW, I only go "down for repair" at the present while I am up here away from home. Once I get back to AZ, and have the space for a home shop etc. I will do all of my own repairs instead of forking out the $ to have someone else do it for me.

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.

Being old won't cause them to fall apart.