How long between major upgrades?

[Stephen Allen]

Way back yonder when I started to learn Linux, for no particular reason 
I chose Fedora Core 3.  Consequently I used FC3 to set up a server for a 
friend's small business, and I used them and FC3 to ply my trade.

Unfortunately, when FC goes to the next version you can't simply point 
the updating tool at the new repositories - you have to point it at the 
legacy repositories.  However, these are rarely updated and I have a 
system woefully out of date.  I can do a system upgrade to FC5 but 
that's always a dodgy move in case it breaks something.

So, I'm learning and testing with FreeBSD 6.1.  What happens when 
FreeBSD goes to 6.2, and then to 7?  What would the upgrade process be like?

Many thanks,
Steve :)