Hello, We are now on Strimmer No 7 - yes 7 in three and a half years ! Why does the line continuously either break or disappear? Each and every time I make sure it is wound the correct way, very tight and uniform as instructed but we just seem to have bad luck all the time. It could be because I am buying the cheaper models (that's because I just know it's going to end up at the tip). Can anyone recommend a good one to buy? I know the principal on all Strimmers is usually the same but if anyone could recommend one which is easy to refill I would appreciate it.