You can decide to save your exiting activities as templates.
Next time that you create an activity, you can select an existing template, which fills automatically all settings for you, leaving you only to inset the dates of the new activity.
How to activate and deactivate templates?
You can activate and deactivate an activity template in settings of that specific activity.
TIP: Make sure you don't save any new activity as template, but only the relevant ones.