You're right, the last 4 months is probably not a good indicator of future use. I had three other tanks (they're gone now) plus a quarantine tank (not set up right now). I also used up a bunch of Prime when I converted this 55 gallon to a planted tank, due to a substrate issue which required me to drain the tank--twice--and move all the livestock into a 20 gallon for two days. Finally, I am getting to the point where I can actually start to enjoy the fruits of my labor!