I have mine listed as a separate item on the home insurance, although the value is honestly pretty difficult/vague. It's a very big and diverse collection, acquired over about thirty years, and if I lost the stuff and wanted to replace it, it could take me another thirty years to track all the models down again!
That's also another problem with insurance; you're paying to insure something that you might be able to replace properly, even with the insurance payout money. If you had a box of LE or unreleased figures for example, replacing them could be almost impossible, and the prices could vary wildly.
One thing to note is that I only value the figures (and some of the books) themselves. I feel that paintjobs that aren't competition-level are probably not worth insuring, and most of us painted the figures ourselves anyway. Not that our time doing so isn't valuable, but rather than we do it for fun and I would therefore find it difficult to estimate that; I would still want to paint a replaced collection if I lost the first one, and that would still eat up my time (again).
Regardless of whether it's itemised under the insurance or not, if you have a reasonable collection, it's probably worth making and keeping some sort of record or inventory of what you actually have. If nothing else, it's a useful tool to know what you've actually got when you are looking to purchase more!