To me, it is something that you need to decide when/if that time comes in terms of the tank leaking, etc. Silicone does not adhere to silicone, therefor you would be basically ripping apart the panles and building the tank back together in order to get a proper seal. People may have other opinions and disagree here, but for me this is everything I have ready and spoke to different manufacturers about and would never try to "re-silicone" a tank.
If you are talking in terms of re-enforcing the silicone after year(s) of use, I would still stick with the above principles. I'd rather replace a tank or have it re-built than to come home to a flood. Just my .02