Paul,
I have three Dolphins at three pools that range in age from 15 years old until January of this year... The oldest one has a bag that is somewhat painful to clean, but not painful enough to replace it yet. The bag allows for a lot of stuff to be picked up..
The one at my house is about 5 years old and has pleated filters that are easy enough to clean, but whole filter assembly does not have a lot of room for a lot of debris. To clean the filter, I have to flip the robot upside down and take out the filter assembly and then remove the filters to clean them.
The new one is an Dolphin S200 and is almost perfect. It appears they combined the advantage of the bag (a lot of room) with the advantage of the pleated filters (easy to clean) into one unit. The filter basket is now removed from the top and cleans in less than 5 minutes, just depending on how OCD you are...
How often you clean them is really a function of what falls into your pool. I would say for most people it will be once a week. The robot can be scheduled to run for a week at a time.. Every day, or every other day, or every three days.
In the summer I tend to only put it in the pool two or three times a week..
Use our search function and enter S200 and see what pops up... The S200 is part of a series... S200, S300, S300i, but the S200 is a rent house and it does not need all the additional features that come on the 'fancy' models.
Thanks,
Jim R.