If your site frequently update with quality content google will crawl your site immediately.In normal sites it will talk 4-5 days. CNN, BCC news crawl by google with in seconds.No need to use fetch option regularly.

Once you upload the website in online, it will crawl for the first time within 2 to 3 days. After that, the crawling will happen depend upon the frequency of content update.

if you want your website to be crawled quickly you should update your website frequently. in this way the rate of crawling will be automatically increased.

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Mostly Google will crawl once in a week that depends upon how frequently you are changing the content on the website.

You need to custom a bot^_^

Google crawls any website so as to get new content. If you will update your blog regularly then Google will also start crawling your site on regular basis BUT When they will feel that you aren't updating your blog then slowly slowly they will also stop crawling your blog.