The seals on my 30g and 27g tanks aren't leaking, but they are wearing out I noticed.. They have algae growing under them and if I put my hands in the tank and rub the seal it isn't attached to the glass anymore.. Some spots are minor some spots the seal is completetly gone right up the middle between the 2 panes of glass.. Im worried the tank might leak one day..
The 30g is about 22 years old and has been running pretty much non stop for 22 years.. Minus the times we moved to a different house and had to take it apart... but yea the pump heater, filter, power head everything is original, Minus the t5 lighting I got. Its a Perfecto tank..
The 27g Hex is about 13-14 years old and its seals are looking pretty bad too, id say 60% of the silicon on all the glass has algae under it now on both tanks.. Its been running non stop as well minus moving of course and all the equipment is original cept the lighting.. Its also a perfecto tank.
Here is a picture of what some of the seals look like.. I imagine it wouldn't be hard to re-seal them, just drain the water down 80-90% and let it dry and cut the old stuff with a razor and re-seal it with clear silicon like you would a bathtub.