Newer hosting providers that cater specifically to WordPress usually have tools in place to ease this pain. I put my clients on Pantheon which has this neat Git-enabled workflow, where code only moves up (from dev to staging to production) and DB stuff only moves down (vice versa from the code). Copying a database from production to staging is one click with their interface. Provided this workflow is respected, this pretty much eliminates the issue of ever messing up the production database, enabling me to always test my changes on a fresh clone of production DB data in either staging on development.
One doesn’t have to use Pantheon – you can adopt a similar approach in your process using your own tools (Git + a DB cloning plugin like WP Migrate DB). I just find this way works well for me.
Question: why would you put your production site in maintenance mode while testing staging? There shouldn’t be a need for that in a majority of cases. The only case I can think of is having some sort of very brittle system highly sensitive to additional user data being fed into it, with a catastrophic bug to boot – but that would likely be indicative of a different, larger, problem where one would need to rethink their product’s entire architecture.