It's hard to cover this concisely, but in captivity ages of over 10 is likely. My oldest female bristlenose is over 7 years old by now, and still breeding. I'd expect the slower growing Peckoltia to age a bit slower and thus live longer. Really slow-growing species like Hypancistrus live even longer - I've heard of Hypancistrus zebra at the age of 18 or so.