It really depends on the type of piercing and long you've had the piercing.
It depends on how fast your body heals, and how long you have had the piercing. The longer you have had the piercing, the longer it will take to close. This is true for all piercings.
Like any piercing, if you take care of the piercing daily and clean it as required, then there is no issue.
It depends on where it is pierced. The lobes can take about 3 months to completely close up, where your cartilage can take 6 months to even a year to completely close up. It also depends on how long you have had the piercing. A piercing that you've had for years can take years to close (in my personal experience).
More then likely they'd have you take out the nostril piercing before they pierce the septum. You should have no problem with the nose ring and septum ring getting caught on each other afterwards though.
It takes as long as it takes once a piercing has healed it depends on haow long you leave the jewellery out, if you are done with the piercing it can take a few days to several weeks for the piercing to actually close once it's a seasoned piercing (seasoned being over a year old).
if its a fresh piercing the hole will close up pretty quickly, if you've had it for a while the hole will probably take a while to close up
After 3 years chances are good it wont close, the piercing will shrink but not close completely.
It varies, if you have had the piercing for a long time the hole might never close. It does vary, i got my ears pierced over 3 years ago and still close overnight.
The length of time you have the piercing for will be three times that period for the piercing marks to close up and disappear.
It will take as long as your body needs to close the piercing, we don't all heal at the same rate so just leave it alone and it will shrink down and close when it's ready.
It depends on where the piercing is. If it's in your nose then if will take a couple hours to close; if it's in your ear then probably a day or two.