Life and salvage are estimates, and they're the cheapest earnings lever in accounting. It takes no transaction and no cash, only a memo to the auditor. Stretch a fleet's life from 10 to 14 years and depreciation drops about 29% on the same base, every year. For the classic US case, look at the airlines. Through the 1980s and 90s, major airlines, Delta among them, repeatedly extended aircraft lives from about 10 toward 20+ years. Each extension lifted profit in a brutally cyclical industry. In India, the FY15 move to Schedule II forced a market-wide recalibration of lives. It's a reminder that any year's profit change can be an estimate change in disguise. You'll find the impact disclosed in the note.
How do analysts check useful life and salvage estimates?
Here's your counter-toolkit. You'll find all the inputs in the PP&E note, and "gross block" means before accumulated depreciation.
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- Depreciation rate = depreciation expense ÷ average gross PP&E. If it falls over time, or runs low against peers with similar assets, that points to lives being stretched. It could also be a mix shift, so check the segments.
- Capex/depreciation. Sustained above 1, it means the asset base is growing or being renewed. Sustained below 1 while management claims growth, it means underinvestment. Or it means yesterday's aggressive capitalization is now producing depreciation that management wants you to ignore.
- Average age ≈ accumulated depreciation ÷ depreciation expense. Average total life ≈ gross PP&E ÷ depreciation expense. Remaining life ≈ net PP&E ÷ depreciation expense. All three assume straight-line and stable prices. They're rough tools, good for trends and peer gaps but not for decimals.
- Salvage games. Raising assumed residuals shrinks the depreciable base. Companies rarely disclose this, so you'll mostly see it through the depreciation-rate trend.
- Fully-depreciated assets still working cut the other way. If the gross block is high and the net block tiny while the business hums, past lives were too short and profits were understated. A capex cliff may also be near.
Worked example: how a life extension flatters EBIT
Mini-calculation you'll reuse. A company shows gross PP&E of ₹3,000 crore and depreciation of ₹165 crore, a rate of 5.5%. Four years ago the rate was 8.0%, and the notes disclose a life extension. At the old rate, depreciation would be ₹240 crore. So EBIT is about ₹75 crore higher than like-for-like, roughly 12 to 13% of reported EBIT of ₹600 crore. You can't prove intent from outside. You can quantify the flattery, compare lives with peers and dock the quality score, and that arithmetic is the job. Outrage isn't.