The frequency and duration of visits varies from one website to another and one search engine from another, too.
It is quite often that we see bots crawling hundreds of web pages from the same website the same day.
The more you will frequently publish new pages and the more your website will get numerous pages (backlinks), the more bots will visit your websites regularly. And that actually makes sense.
Google Webmaster Tools service will provide you statistics about the crawling of your website by Google Bot.
