Time to SLA add-on listens all issue events and re-calculates SLAs at each issue event. This provides consistency across all issues for all SLAs. However there might be some projects or issue types you never apply SLAs on and it might be a good idea to completely exclude them from SLA calculation rather than excluding them with JQL in each SLA definition.
TTS allow you to include or exclude any project or issue type from SLA calculation. Simply go to Time to SLA menu > Advanced Configuration > SLA Calculation.
In this page:
White List: If you would like narrow down your SLA calculation scope into some set of projects and issue types then you can add as whitelist rules. Keep in mind that once you defined whitelist rules any issue that does not fit those rules will be excluded from SLA calculation.
Blacklist: Alternatively you can put projects or issue types in blacklist so that any issue matching those rules will be excluded from SLA calculation.
If you use Whitelist and Blacklist rules together blacklist rules will precede whitelist rules.