Reducing the per period metrics displayed and / or Number of Periods can help in optimizing performance.
For Monthly views, it's recommended to only show 12 months in the TSV at a time
Add data metrics as Totals in the Assignments Grid instead of showing in the TSV whenever applicable
Additionally, in 15.9.2 you can control whether Totals are a Sum of the fiscal periods in the view or Grand Totals (Sum of all Periods for the investment). This allows you to still have the grand total even when not all periods are displayed on the screen. This option can be set in View Options in the Totals Column section
Utilize the Scrolling Carousel (Widget) (Starting in 15.9.2)
This new feature allows users to scroll through selected fiscal periods easily without having to modify periods in View Options.
Paste by row instead of by column
Pasting by row versus column is recommended to optimize performance when using the paste feature to make updates to cells
Use Bulk Update (Available starting in 15.9.2)
This feature allows you to edit multiple rows at the same time for changes that are the same for each row. (Example, adding 8 hours of ETC per assignment)
To utilize this feature, click the check box next to the rows you want to Edit, then click the Edit button that displays.
Bulk Edit will perform faster and keep the user updated when the update is still in progress