What is a typical lifespan for a sump pump?
The life span of a pump is hard to evaluate, yes constant cycling can shorten the life but it’s usually the float switch that fails. 
The quality of the pump is a major factor in life span a quality brass housing with sealed bearings is going to outlast a plastic housed pump in most cases but not all. The water being pumped is the next thing is it clear? Dirty or even muddy. Clear water with a normal ph will be the easiest on a pump, with muddy water eroding the impeller and housing. 
What is the “head” the pump needs to pump, how many feet is the water being raised the higher the head pressure the harder the pump has to work. 
The size of the sump pit and flow needed to keep the basement dry
If you have a 10 gallon pit the pump will cycle more often than a 55 gallon pit even with a small pit if your pump is cycling two often a better choice can be a smaller pump that runs longer (you always want a cycle or on a heavy day the pit will over flow) I know of several homes that have 2 pumps a smaller one for most of the time then a large one for the heavy days with the large pump being set to cycle above the small ones set points so it cycles less often and prevents flooding if the small pump is not keeping up this method extends the pumps life and reduces energy costs in homes that have more than winter high water issues. 

So there are many reasons it is hard to find an answer perfect sizing and setup may last ~8-10 years +-. Most pumps last a few years, keeping the pit clean of sediment and adjusting the cycle time with a properly sized pump will give the longest life. This is in my area that when we need them they are used most of the year.