keg question

[gufbal]

my co2 tank is empty but i still have beer in keg should i untap until i get co2 refill?

1 st time my tank has been empty

 

[CBMbrewer]

It shouldn't matter as long as you don't serve any beer from it.

 

[Danno81]

I woke up this morning to a empty tank. I think one of my seals is leaking. I exchanged for a new tank and put pressure back on the keg and turned the tank back off my question is how many kegs can I get out of one 5lb co2 tank? I know with commercial bought kegs I was getting 3-5 depending on the size of keg.