Power Amp


My power amp keeps burning up the power tubes.  I get maybe 4 months out of them  . I have use three different type of tubes that are recommended for the amp. Can anyone help, why this is happening, are all of the power tubes bad?
128x128mcallij1
Hello,
I hate that I have to ask. Do you leave your amp on all the time? That recommendation is for Solid State only. Tube amps are turned at about 15 minutes to 30 minutes before use or pushing the amp. Basically warm up time. Please do not leave your amp on all the time. If it is not that then send back to manufacturer. 
I had solid state amps and sold them off. Wanted to get a tube amp a chance ,keeps blowing the power tubes . It does not sound like a tube problem but a amp problem. Thanks for all the responses.