The default auto-save interval in Vegas Pro is 5 minutes. The default interval is reasonable, but it can be changed if required.
Changing Internal Preferences
In order to change the auto-save interval, you need to access Vegas Pro’s internal preferences which are hidden by default. Changing internal preferences is somewhat risky, which is obviously why they are hidden. When changing internal preferences it is better to keep a record of the items you have changed in something like a text file. Vegas shows the current value and the default value side by side for each item in internal preference, so if something goes wrong you should be able to change the value back to default. If you don’t remember which internal preference item was changed then you will be forced to reset all preferences, both internal and non-internal to default.
Coming back to the auto-save interval setting, changing this setting should be safe. But setting the interval too low can affect the performance of Vegas.
Here is a video showing all the steps