I suppose I'm a bit of a hack,too. Unless one is using the equipment professionally where downtime is money lost,run it till it drops dead,then replace it with an 'all parts totally new' engine. All this saying keeping up good maintenance,oil changes,air filters,etc. There is that school of thought that it is much faster to replace with new,rather than wait for going the rebuild route,especeilly if there are clients to contend with. Have a replacement on the shelf, and have time to get the original one tended to This,of course ,does not apply to rare one of a kind or special engines.