The more lines (Max i would say 3) the better Your service! Especially when watching Big PPV events!
Secure and Stable Servers only go down for a few seconds each night between 00:00-05:00hrs as a critical reboot is required to optimise the system, 2 servers in same box means You won't see this either as the 2nd line cuts instantly in to cover.
The main reason lines glitch or fail is over subscription, there are lots of dodgy sellers who just sell the same server over and over or the same line sometimes, make their money and run leaving people high n dry!
Feel free to PM Me for more info if You need it :)