[MyNameIsFred]

I'm coming from the Java world, but as a consultant for enterprise customers, I'll say that they only understand two kinds of ongoing maintenance: 1. Dollars over time (e.g. licenses) 2. Purpose-specific hire (i.e. hire a guy to do nothing but support this new thing between now and forever)

In other words, they understand continuous maintenance, but not continual maintenance. Anything else is either too awkward to write on a budget. If you suggest that it needs periodic review, they'll think you just need to "do it right the first time, so this isn't an issue going forward", whether or not that makes any sense.