I haven't installed LEAP yet, but I want to know how would it function given the following:

If I have a certain electricity demand to be met through a certain generation mix (RE, fossil fuels...) and LEAP would optimize the generation mix based on the least cost method. In one of the years, say that the demand was met already, does LEAP chooses between retiring some of the current operating plants (with its relative depreciation price and the OPEX) and building a new power plant with its consecutive costs (OPEX, CAPEX..).

Note: I have the data for OPEX, CAPEX, retirement age, lead time, efficiency, and availability of the powerplants

It doesn’t actually retire plants until their lifetime is up, but the optimization algorithm may simply not use them if an alternative is cheaper.