Are your rail trails paved or unpaved?
Can you change a tire if your life depended on it?

40 miles rides are getting to be pretty long rides.

I think I would consider one of the Mixte bikes. There are quite a few old ones around, that could be picked up cheaply on Craigslist, and either ridden, restored, or rebuilt. However, I believe a couple of brands are still making them.
Viva Legato 7 Mixte Step Through
Adrenaline Bikes Soma Mixte
Adrenaline Bikes Soma Mixte Custom

As far as "the last bike ever". Some of the cheaper bikes have low end bearings that wear quicker, especially if you're putting a lot of miles on the bikes. Perhaps other cheap components. So, bargain may not equate to longevity.