Oak fermenting vat questions

Winemaking
1

First question: Where is the least expensive place to get oak fermenting vats in the USA / company to source them from?

Second question: How long will oak vats last for? I’ve heard everything from 25 to 100 years. If you use a vat seasonally (i.e. every fall and winter, but not spring and summer) will it last less long?

2

One must ask one self;
Why is the person who has the oak barrell selling the oak barrel?!

Get oak chips or staff & stick em in your glass/plastic carboy. same think less maint.