I agree with
@OliveFish05 .
There are many factors that determine how long a person is keeping fish.
For me, there are a few main factors:
1)Availability of time
Some people due to their busy schedule are unable to keep fish especially when they have just started a family.
The fish that require the least maintenance is probably a single Betta in a big tank but it won't be so interesting to only have one fish in a tank.
Some people have ponds in their house where they will keep their Koi or Goldfish for a long time.
Koi can live up to 20-30 years.
2)Is the person making a living from keeping fish?
This is totally different from someone who is keeping fish as a hobby.
3)How strong is the person interest in keeping fish?
Some people keep fish for their young children. When their children grown up, they will stop keeping fish.
But for those who are passionate about keeping fish, they often have a few tanks in their house and not just one tank.
4)Cost
In my country, fish are cheap but the medications are quite expensive.
Marine fish with reef will be more expensive and require more maintenance.
But those who keep marine fish or fish with reef may not give up this hobby easily since the marine fish and reef are so beautiful.
For those who can afford, they will keep Marine fish with reef, Arowana and Stingray for a long time.
Lastly, I think your question should be "which is the most common tank?".
To this question, I think a community tank is still the most common but how long they keep the tank will depend on the above factors.