Subtitle Studio 2.0 includes possiblity to split one big subtitle file into two.

Spliting Files :

1. Add Breakpoint by selecting arbitrary checkbox
2. Select 'Split' Tab
3. If you want to keep original values don't select 'Recalculate Values' (see Example 1 for details)
5. Click 'Split (Including Breakpoint Up)' or 'Split (Excluding Breakpoint Down)'
6. Click 'Switch to Next Part' to cycle between Part 1 and Part 2

Advanced Split :