Ameritron AL-811HXCE back to life

Good news !!! - just acquired from eBay four RCA - NOS (new old stock) 811A 's from a UK seller - I got hold of some russian ones a month or so back just in case - but RCA at a good price (and I do mean good - thanks nick!) I couldn't pass them up could I ? 

Hope the arrive safely, (and work of course!) but that a risk from wherever I got them from.

Anyone out there have any advice on how to "burn them in" - or whatever the equivalent is ? 

Now just go to get on with fixing the amp :)