You've Got the Capital
If you're busy, you've probably got a nice influx of cash coming in. The cost of of a video is variable depending on the quality of the production-- you get what you pay for. So if you've got the money now to invest in a higher end video, there's no reason to wait.
You'll Have Access to Outstanding Testimonials
If you own a service business, testimonials are a fantastic way to help bring in new clients. When you're company is busy, you're likely surrounded by happy customers who can give you great recommendations. You'll want to catch them while their experience is fresh in their minds and they're excited about what you did for them. The busier you are at the moment, the bigger the pool of potential testimonials and the choosier you can be about who you ask to represent your business.
You'll Be Ahead of the Game
What goes up must come down. Every industry experiences dips, and you don't want to get caught off guard when the next one arrives. If you've already got a marketing video in your back pocket, you'll be better able to head off a slow period, and get your business booming again!