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?
mcallij1
Yeah, something is wrong with the amp....most likely the power tube auto biasing section of it.
It has auto bias, Do not want to name the brand yet, amp is being repaired. Keep getting told it is the tubes, looking for other opinions.