LTV/CAC Ratio: How to Calculate Customer Lifetime Value 

Hi, I have a quick question, how would LTV be most optimally used for businesses that sell products that are generally bought about one or very few times? So, unsought products. Let's say for an exotic car rental business, where customers might only once come in and rent out a Lamborghini, or very rarely do so. Hope this example makes sense, but I'd just like to wrap my head around this concept better and see how calculating an LTV:CAC would be done in such a case, and if it would be a useful metric. PS: Is the average years number a guesstimate? Or would a business ideally look at all of its customer base, count the years they're s customer, and average it out across that same customer base? Thanks!