I second this. There isn't a whole lot to be gained from inspections save from identfying catastrophic failure of the belt itself. The issue generally lies within one of the bearings or the tensioner or the waterpump seizing up and shreding the belt.Inspections don't help much unless a tooth is missing or something else real obvious, otherwise they appear okay.
When all esle fails, read the owners manual / instructions!Have you read your owners manual? The interval should be in there.