This, and sales concentration is a real risk as well. If you have few big customers and even one of them churns, the impact this will have on you is certainly going to be material.
Yes, the strategy for big client is to lock them in for long engagement (like a 3-YR term). Throw in some nice support package, longer trial period, whatever. Since big customers often take months to fully use a product (6-12 months is very common), I wouldn't worry about "oh now I got big name, I need more infrastructure, more money to pay my cloud vendor." It won't for 6-12 months and you probably can keep all the pennies from the big client monthly. If you get a downpayment (say 1-year for a 3-yr term), you get ammunition to grow your team and get more smaller customers.