I have had deWalt and Milwaukee Lithium battery packs, I have noticed that the batteries lose run time as the number of charging cycles increase. Lithium are much improved over the Nicad batteries. I am wondering if for example I run a 19 inch lawn mower say 15 to 20 times a season, will i have to replace the batteries every year or will they last 2 seasons, If I would ever change to an battery powered mower I would have to consider the cost of replacement batteries.