Why does the ADS Straight Line Mid Month method for USA tax registers only show very long effective life options of 27.5, 31.5 and 39 years in the drop down options?
The reason the ADS Straight Line Mid Month method for tax depreciation in the USA only has 3 very long effective life options is that this method typically applies to long-life assets like real estate / property.
Perhaps select a different straight line method, for example ADS Mid Quarter and Mid Year.
The GDS Mid Quarter and Mid Year Straight Line Methods all support much shorter fixed asset effective lives.
For tax depreciation methods in the USA, you also have the option of choosing Section 179 as your tax method.