create separate search service applications for big content sources and best practise for crawling settings?

Question

In our SharePoint farm it has 4 big Content Source Web Applications around 3 TB of documents and daily users upload documents around 5 - 10,000 documents, and i need to run incremental crawling every day every 30 minutes and full crawling every weekend,

1. Can i create separate Search Service Applications for big content sources is good idea?
2. What is the best practise to run full crawl and incremental crawl like above scenario in our sharepoint farm?

This farm has two separate crawl servers Below is the number of searchable items:

Answer 1

1) Unless you are splitting your content into different farms, adding more processes (new Service Application) to run on the same farm (servers) will only increase the load.

2)

• a) Full crawl - needs to be run only when you are aware of changes to document properties. E.g. there is a requirement to add new managed properties or change existing managed properties.
• b) Incremental Crawl - This depends on the content refresh rate expected by the business. Here is where you have to intelligently segregate your content stores and update the incremental crawl schedule. For archives and records, once a day should be sufficient. Again, this is based on business needs.