there are a bunch of reasons that this could effect lifespan... The genetics of most morphs arent fully understood much less how those genes work in tandom with other mutations. Also again for most morphs you have a very very small initial gene pool. (All "Lessers" originate from 1 animal right?). There is an assumption that these genes only impact color/pattern but the truth is nobody actually knows for sure. Not to mention "hidden" attributes
I know only time will tell, I was just wondering because I've never seen the issue talked about.