You won the job with a great 1st Date (aka Spec Review), but no marriage can last without ongoing effort.
Left to their own devices, most developers will slowly make more and more unmaintainable code, that is only comprehendable by themselves. This isn't a big problem for them as they are in it every day and know how it all fits together, but if they're not coding to a set of industry standards, you'll find this code very hard for anyone else to maintain.
❌ Figure: Bad Example - Would you want to maintain this code?
This can be fixed by having regular software audits with a Solution Architect to keep the developers accountable.
Each month, the Account Managers call all their current clients that have had a substantial amount of work done and offer them a Software Review.
This makes more maintainable software with better architecture using industry standards.
More information: The process:
Figure: A sample report to see your top clients