If you do not clean the hot tub filters, two things can happen - firstly, this is bound to happen in the short run, the filter will get clogged and it will lead to the water in your hot tub getting dirty and not getting cleaned. Next, the clogged spa filters will lead to a slow inflow of water, which will lead to the heater shutting off or slowing down, and will cause an impact in the pump and pipes which will be performing at a normal capacity - leading to major damages in various parts of the tub. This is something that is totally avoidable if you ensure that you are cleaning your spa filters on time.