Andrew D. - When the seal goes, the pump will leak water. So your tank will loose water and it will be on your floor. The leak can also damage the shaft or the bearings.
in my case the seals corroded and that wear damaged the motor shaft. If you are seeing any salt creep or a leak you are on borrowed time. I would order a set of seals and have a back up plan.
If I keep using a Reeflo pump, the seals are getting replaced every two years.