Blown tube issue

So one of my Tung Sol EL34s blew last weekend after 6 months and I’m not running them constantly. Manley is replacing for me.

My question is : is it ok to pop in a random EL34 in the interim and how does that affect sound ? Same brand better ? These tubes I bought from Manley are all bias numbered . Not sure if there is an exact slot order to the numeration . 
Another thing that concerns me is I bought the snappers used from some Agon user who replaced/upgraded the caps . I’ve been told depending on his work this could be the reason I’ve already blown 2 power tubes in 1.5 years ? Anything I can be aware of appreciated !

my setup :
manley snappers
Manley jumbo shrimp pre
VPI super prime scout
allnic h1202 phonostage