Once created for each individual asset, the asset entry worksheets will carry forward in TurboTax from year to year until you dispose of the asset. Generally, you should not have to interact with these worksheets during the life of the asset. They work in background, providing TurboTax with the data needed to calculate your annual depreciation expense.
When you purchase a new asset, a worksheet needs to be created for it, either through the EasyStep interview or directly in forms mode. Forms mode is only recommended for users who know their way around the tax forms with a high level of expertise.
Your question did not state what specific task you are trying to accomplish that causes you to think you need a different form, only that you have an asset that has been depreciated for three years. If you are disposing of this asset, the disposition information would indeed be entered on the worksheet, to complete Form 4797, and determine gain (loss) on the business asset.
