One reason that many freelancers burn out is because they offer services, but not products. Services tend to be customized to the client’s need and billed by the hour. Products are customized by you and sold for a flat rate. Products also create the opportunity to create a repeatable process that can be streamlined as you sell more. This means your margins can increase as you are able to work more efficiently and eliminate or automate some of the administrative work that typically goes into services.
If I were to get into freelancing again I’d absolutely structure my services as a product.
Everything else — the labour, the method, the work that gets done to deliver the product — becomes a system to refine and scale over time.