Lifetime value is what a customer is worth across the whole relationship, not on the job that brought them in.
A one-off repair worth $300 and a maintenance customer worth $300 a year for eight years are the same first invoice and very different customers.
Why it decides what you can spend
What you can afford to pay to win a customer depends on what they are worth once you have them. A business that only counts the first job will always conclude that advertising is too expensive, because it is comparing the cost of acquisition against a fraction of the return.
What raises it
Repeat work, service agreements, and referrals. Each of those is cheaper than finding a new customer, which is why an existing customer who is not being contacted again is the most commonly wasted asset in a service business.
The caution
High lifetime value concentrated in a few customers is not the same as a healthy business. Read it next to customer concentration: if the valuable customers are also the only customers, the risk is larger than the value.