Well, I’ve had my stock strap on my Canon EOS 400D since I got it (Three years ago), and I’ve changed the way it hangs about two times in total, switching after the first year. The strap doesn’t seem to be in too bad condition, some of the fibres look a little warped at the strap loop point, but I’d rather replace it before it snaps. Keep in mind I do use a 16-35 L lens as my main lens and frequently pair it with a 430 flash, so it’s not a completely unfounded concern.
I’ve seen many after-market straps, from Lowepro to obscure brands, and it seems that regardless of whoever makes them, they all have quick release neoprene straps that seem very ergonomic. I’m always scared that if I were to use one either the quick release would do it’s thing without me wanting it to and my camera dropping and smashing, or that the neoprene would just tear (I’ve always assumed the camera bounces slightly when you walk with a neoprene strap). Lowepro’s lifetime warranty isn’t that comforting when it doesn’t cover what their product was attached to

My questions:
How many years should one typically use a single strap for?
Are quick release straps safe?