I have a website with over 4,00,000 pages and i have created 10 sitemaps with 40,000 links in each site dynamically with php and submitted it in my google webmasters account , i add 50 - 60 pages to my website daily and i don't want to create another sitemap after every 40,000 links now . I have a solution in mind for this which is making a sitemap dynamically which shows all the links to pages created with in last 30 days now and re-submitting it everyday once (with a cron job) but here's the problem the pages i have created before last 30 days will not be in any of the sitemaps so i wanna know is if the links are indexed by google and after resubmitting the sitemap if the links are not in the sitemap will they get unindexed ? and if yes i would really like to know the solution for this ..
I am kind of beginner in seo so if it's a bad question i am really sorry but i searched alot before posting this question but couldn't find any solution.