Nicholson, Sandvik, Simonds and Grobet are all good files. Used hundreds of them over the years in the machining industry.
Take good care of your file and it will last much longer than if you don't. Before use clean it with acetone or aerosol contact cleaner, let the solvent evaporate or blow it off with compressed air, chalk it up with any old stick chalk and brush the filings out with a fine wire brush or file card as you use it. Never touch the teeth with your oily fingers. Remember most of all files are like a hacksaw.... they only cut on the forward stroke, do not drag it backwards or you will dull it faster.
When the job is done brush the file good to clean it, then lightly coat it with WD40 so it will not rust. Rust KILLS a file !!! JMHO