Light boots for 18 hour days .

Lately I’ve been working 2 or 3 jobs a day , 95 % of which is spent walking ,
and moving equipment around . I need a comfortable pair of lightweight
mid height boots . Ecco walking shoes aren’t bad , but any suggestions
to help my aging feet are gratefully accepted . No rough terrain , just
grassy fields , and concrete surfaces .

Check out pretty much any Salomon Boot/Hiking shoe.

I know you don't need anything for rough terrain, but I have hiked and average of 10+ miles/day over long periods of time in Salomon Quest 4D Forces. They also make a gortex in the same boot, but unless you're somewhere pretty cold, the gtx variation gets pretty hot.
 
Take a look at Zamberlan boots. Have three pair. Use them for backpacking, hiking, walking, and range wear. Hands down the most comfortable boots I've ever worn and I've owned Lowas, Asolos, and Salomons. Extremely well made. My feet never get tired in them.
 
If your getting in and out of equipment all day long at jobsites that are likely muddy, you sure won't want any boot with lugs or added traction. All they do is hold mud and get heavy as well as track it into cabs. Smoother the tread pattern the better. This is the main reason why I don't wear hiking boots when running equipment. They hold onto mud.


Bingo. Exactly right. Here in tx it's ariat cowboy boots for construction
 
Get orthotics and waterever boots fit. If your feet hurt you need an orthopedist or non-quack podiatrist. You need a stable base.

Glued and plastic lightweights are use for however long and dispose. Even if you spend $100 to glue a new sole on it won’t be trustworthy.

Traditional sewn boots are heavier but can be resoled and go on for many years, hard to ruin a leather upper.