Yes, google keeps track of changes in your pages over time, and if they almost never change, it is likely to crawl the site less and therefore update less.
You should be able to find out more by looking at the google webmaster tools (crawl rate). My site is crawled at the rate of tens of thousands of pages per day, which means google is usually right up to date on indexing it. That is because google knows things change by the minute on Hearth.com