The most commonly used email templates are active daily. For those templates more rarely used you will need to activate & deactivate when needed.
Note not everyone has access to these templates.
Email Templates Section
Profile > Settings > Setup > General Settings > Communications Templates (near the bottom of the list)
Custom Templates
Across the top will have option for different types if templates. You will want to select Custom.
Active On OR Off
Now you will be able to see the subject & description of each template.
Select the edit (pencil) then make the template active or not active.