Unfortunately the part you can't predict is when you'll really need an aftermarket damper. Many people remove the stock damper, flush the oil out of it and fill it with straight 90w oil to make it stiffer.
If you're truly just riding it on the street, not wheeling all over the place and burning the turns on the ragged edge, you should be fine not touching the stock damper.
If you feel safer with an aftermarket damper, there's many choices and prices. I recently purchased the Hyperpro RSC active damper, at the moment I didn't find anything that is up to date as this one. Not cheap, $400+, but I had a seriously close call a few weeks ago drag racing so I needed to do something more for my piece of mind then anything. Come to find out when I removed the stock damper, it was bad, thus not stopping the violent tank slapper that nearly tossed me right off the bike at about 115mph.
Lots of choices out there, just depends what you're doing with the bike.