While it is a good way to go, it isn't the only way. It is expensive, relative to internal sealant, but foam does last for the life of the tire. I was paying $25 or more each time I got a flat on the front of my JD 870. That was bad enough, but I usually lost most of a weekend due to the flat. I figure that I have saved money since I foam filled the front tires, based on historical frequency of flats and the cost of repair.Foam filling is the only way to go. Just make sure to specify the psi you want them filled to.
Works excellent on tractor front tires for extra weight also.
The rears? That's another story. One flat in nearly ten years and an estimate of $600 each to fill them. They get internal sealant.
YMMV.
Matthew