What should I look out for with my maintenance agreement?

You should review your maintenance contract with your installer to ensure there is clarity about the costs, what they will deliver and how/how often.  Be aware of the requirements relating to terminating your maintenance contract (e.g. notice period), and what is and is not included in the contract.

Generally speaking, an ordinary service or maintenance contract covers functional testing at regular intervals, but not equipment upgrades, repair or replacement parts. So-called comprehensive contracts may include these additional things.