When buying an automatic lawnmower make sure that there is at least a two year guarantee. This will obviously not cover any damage inflicted by negligence on your part. The fact that this guarantee is in place shows that the manufacturer is confident in the performance of his automatic lawnmowing system and should put your mind at rest that you are choosing the right make of automatic mower.
These robotic lawnmowers will be trouble free for years providing common sense is used. There is very little to go wrong as they basically consist of wheels, a casing and a machine that works like a computer - and of course the blade driven by the motor. (Notice I said 'blade' and not 'blades'). Most of the servicing and repairs will take place in the same manner as the modern cars use - by plugging into a computer with special software that will identify any problem and indicate how to put it right.
The kind of accidents that could happen are so easily avoided. Make sure the edge of the lawn has not been trimmed away to neaten the would mean that the cable (which encloses the area to be mown) has not now become too near this edge; if it is the robot could go over the designated line and hit, say a birdbath. This impact could chip the blade.
This happened to my automatic lawnmower as my garden help forgot I used an automatic lawnmower and neatened the edge by a few inches; result - my blade had to be replaced. If you buy the type of automatic lawnmower that only has one star shaped blade this is easily replaced by yourself at very little cost.
The drawback of a robotic mower having two or three blades is that the grass clippings can get clogged in between and put strain on the motor.
Any large, solid object on the lawn will present no problem as the automatic lawnmower will gently hit it and move off in another direction. Trees, island beds and ponds also present no problems as full instructions as to how to lay out the cable and set up the charging station are sent with each automatic lawnmower. In fact, if you wanted one, a trained technician would come and set up the whole system for you at very reasonable cost.