Self-sharpening blades are the most consequential and least marketed specification in trimmers. The principle is simple: the blade pair is ground so the moving blade continuously hones the fixed one as it oscillates, meaning the cutting edge maintains itself instead of degrading. Philips calls its implementation DuraPower and DualCut; Panasonic achieves the same effect through nanopolished edge geometry. Either way the outcome is a trimmer that cuts as well in year four as in week one, with no oil and no replacement blades.
Set against the alternative, this is where the real cost of a trimmer lives. Titanium-coated blades — Mi, Havells, boAt, Vega, Syska — are a genuine step up from bare steel and give two to three good years before decline. Uncoated stainless on sub-₹700 trimmers is blunt within twelve months and cannot usefully be re-bladed. Neither can be sharpened at home, so declining cut quality is permanent.
Run the five-year arithmetic and the recommendation writes itself. A ₹949 Philips BT1232 with self-sharpening blades costs ₹949 over five years. A ₹549 Nova replaced three times costs about ₹1,650 and cuts worse throughout. A Philips OneBlade, by contrast, is the outlier in the other direction — an excellent device whose blades are deliberate consumables at roughly ₹2,700 a year, which is the one thing to understand before buying it.