Yep thats the only way to find out the longevity of each of your fish is know the name of each fish breed you have. Then google search by that name, thats also a good way to get tips for caring for them, their tempature requirements ect.
Thats how I found out my Pleco has 15yrs life expectancy and he is now bout 12yrs in my tank. Plus however old he was before I got him.
But keep in mind, a well kept fish like humans can out live expectations

Gold fish are given 3-5yrs approx longevity, but in my first 16ltr tank I had 3 that reached 12yrs!