[time-nuts] how long dues this rubidium standard last for

[Paul Bicknell]

Hi all 
as I am new to time nuts could someone please help with e following 

questions 

I have a Racal 9475 and a comment was it is a good entry level rubidium
That is not working yet 
how long dues the rubidium standard last for and how much to replace	? 

I assume rubidium & cesium's are left on 24/7
?

I think I would like a HP 5065 
so how long dues this rubidium standard last for
?
and how much to replace
?


regarding the HP 5065 how much am I going to have to pay for one
?

I want to also do the Corby Dawson optical window modification 
so How much is the new optical window
?

I realise the are a lot of questions but any answers would be welcome 

Regards Paul B