So after 10 years with my '50 N, finally got a flat up front back in the spring. The other side was still holding air, but looked worse, so I got two new tires and tubes.
The local tire place, which does do tractor tires from time to time told me the rims were really badly corroded inside and they'd lined the inside with duck tape to try to protect the tubes.
Well on one side it was needing inflation monthly, the other side was holding fine. So I used "Fix-a-flat" on the one side, and actually that side is now holding fine. But this last week the other side died, and the Fix-a-flat trick didn't work, at all.
I'll get new tubes, the new tires should still be fine.
My options are to get a couple new rims, looks like $60 each on eBay, or remove the current ones and grind them down inside so the tubes don't get punctured.
I will also take the opportunity to renew the bearing assemblies, which were badly worn, but made it through the mowing season OK.
What's the advice ?
And oh yes, Merry Christmas !