A made a 12 month proposal for a SEO services for a website that streams music. It currently has around 5k artists and 50k tracks that need to be optimized. The client told me that they want to sign up a shorter contract and if they see results, we will continue working together. How to explain to them that SEO takes time and I need 1 year to execute the strategy properly?
Pivot—they don't trust you yet, so you need to build their trust first.
Offer an initial "paid discovery" project, instead of pushing a long-term contract before they're ready to commit. They can see the quality of your strategy work, and you and they can decide if you want to continue to a strategy and implementation retainer.
With paid discovery, you'll get paid (good), and they get a concrete deliverable (also good). For SEO agencies, paid discovery typically involves doing an audit, but you could also outline an initial strategy for (for example) their most-lucrative artist.
Ultimately, you'll also learn what you're getting into before you commit, too—50,000+ pages is a lot to optimize.
And then improve your agency's own marketing (including positioning, testimonials, case studies, and other social proof). SEO clients are happier to sign long-term contracts when they already trust that your agency is the perfect match for them.
Want advice on that? I'm glad to do a Clarity call to help. Good luck!