Energy can neither be created nor destroyed only one form converts into other. Hence we can say that life is endless, only transformation and conversion occurs.
microbes themselves can be tested and the term is "BioBurden", or microbial limit testing, how long microbes exist without sterilization. Genetically speaking one particular strand of microbe can go into senescence however, microbes tend to evolve and adapt. Life is endless, even on a microbial level.