When to create additional views
Most pages create and register just one view named 'default'. This is quite OK for simple pages. For complicated pages which handle multiple event combinations it can become a burden to create and maintain single large TPL file with many IFs to switch what to show and what to hide.
Create additional views:
- to reflect different modes in which WP operates.
- to use with different event handling methods. 1:1 is good ratio in this case
- to split large TPL files. Usually large TPL files are result of not following previous rule. Some lazy developers tend to use single view and export variable like "$mode" and check it and switch accordingly to show large chunks of HTML. If you have {if}s topmost in your TPL file - probably it is good idea to split the file if it is large.