There seems to have been no drop in efficiency since then. As well as grinding, I also use it to clean. I started by using a screwdriver that came with a charger and two batteries for 5A, and then I switched to a naked angle grinder carcass because, frankly, it's a pain to have to buy and haul around two luggage, two chargers, and four batteries. When I originally considered bringing along a screwdriver powered by 2A batteries, the shopkeepers gave me sound advice, assuring me that the batteries would survive for at least a few minutes while using the angle grinder. Using a disk, stripping, and just buzzing at idle with periodic replacement of cut components, I found that the 5A batteries lasted an average of 20 minutes, with the mode and load having absolutely no influence on the operating time. I use discs that are 1-1.2 mm thick for cutting. There are times when working with no string and electricity is not just cool, but crucial. Absolutely delighted with the acquisition!