lol loan = lone
Guessing if meaning left on your own
Finally someone picked up on that. Yep pretty sure he meant alone too.
As for that, it really depends what his meant by alone, if you mean leaving the house entirely, but going to another room can be ok, as long as you're careful. I wouldn't leave someone alone while gagged as well, need them to be able to call out if anything does go wrong. Otherwise you need to think up some intricate way of being notified by the bound person if there's a problem.
As for how long, until it becomes too uncomfortable or the person binding gets bored of not having use of your hands and mouth
(also check the cuffs are loose enough not to start cutting off circulation and check on the restrained persons circulation regularly.
With the gag part for how long as well it's good to remember that certian gags, ball gags especially cause the wearer to drool, so you need to be careful what position you have them in especially if you're planning on leaving them alone, you don't want their mouth filling with drool.