I would be in the same boat, but I have found that a Moto G with a prepaid SIM is a good middle point. Just cheap enough phone I can afford to have it stolen, and still with the Smartphone features that make me want and need a smartphone. (Navigation and messaging).
Yeah, I haven't looked into cheap smartphones (I bought my current dumbphone maybe two years ago and things move quickly).
But of course at time goes buy the low end phones get more and more featureful. That being said I doubt the Moto G has 10 days battery life and is as solid as my current brick phone.
Still, it's a good recommendation, I'll look into it when my current phone stops working.
It absolutely does not have 10 day battery, but it does have one of the best battery lives of the crop. If mostly left asleep, it could last several days for sure.
I do grimace more when I drop it onto a stone floor, but it has already survived that once.