I have a bladder tank and twice a year or so I have to add air. About a year ago, I researched new bladder tanks and found they and the non-bladders are priced reasonably. Just in case my bladder goes...I bought this Sears tank maybe 35 years ago for less than $100 and it's still going. Of course, not available at Sears now.
I have checked the air valve and etc on my tank and cannot detect air leakage. It must be so slow that it takes nearly a year to completely empty [the bladder]. It is a maintenance item, check the air pressure. I have no experience with a bladderless tank.