The step to take before spending anything: find out whether there is a repairer near you and what they will and will not do.
The whole case rests on the resole actually happening, and for a lot of people it turns out to be a two hour drive or a postal service, which changes the maths and changes the likelihood of bothering.
Worth asking them:
What do you charge for a full resole, on the kind of boot you are considering.
Which brands do you see and which are straightforward. Repairers have very direct opinions about this and they are worth more than any review.
How many times can this be done before the upper is the limit.
That last one matters, because the sole is not the only thing that wears. The upper leather cracks at the flex point, the lining wears through at the heel, the eyelets tear. A boot is resoleable until the upper gives up, and how long that takes depends far more on care than on price.
So the realistic version is not decades from any boot. It is that a well-made pair, looked after, resoled twice, might give you eight to twelve years - against three or four pairs of cheap ones in the same time.