Any decent portable should run 50foot, i run 50 as standard and extend to 75foot when needed.
There's guys on here with top end portables that run 100foot as standard.
By decent portable i mean, minimum of 2vacs and 100psi, if yours is any less than that, dont get a second hose, and if possible you really need to think about changing machine.
If it is, then 50foot should be fine and that will do most houses with the machine left at the front door.