AFAIK, unless this was changed in DF2010, if you get a king, "Abandon the Fortress" is replaced with something along the lines of "Yield power to the king/queen", and your fortress stays on the world map, and the dwarves stay at your fortress. The fortress is both reclaimable (I think), and you can explore it in adventure mode, and found a new, different fortress, and make *that* the mountainhomes too!!
Otherwise, if you don't have a king/queen, then you can just "Abandon the fortress". Your dwarves all leave for nearby dwarven settlements (or just hang around the fortress), and you can make another fortress, or you can reclaim the old fortress.
If you are under siege, then you have to "succumb to the siege" which kills all your dwarves. But again, you can reclaim, or you can make a totally new fortress.
What you are asking for is impossible (world gen stops when you start your first fort / adventurer): To have your old fortress constantly make new goods. But you can have multiple fortresses on the same world map, without regenning. You can keep your old pantheons and civs, and still explore different lands, biomes, and different underground sections
The fortresses are self-sufficent if you release power to a king/queen, just like a regular mountain home, but they are not attached to homes, don't plant farms, etc. etc. etc. Your dwarves hold everything they use to have (so your axedwarf will still have his axe and armour if you look in adventure mode again), if you release power or abandon. If you succumb to a siege, then the corpse will have that armour / weapons (I think. They may be scattered around as well)
Oh, and when you release power / abandon / succumb to siege, then your goods are scattered throughout the embark site (heavier goods move less)