What is the common consensus on the average lifespan for the 2 IS Alternator in miles. I have seen many replace them around 110-120K Miles.

 

That is a pretty average lifespan for them if we just go off the sample of people here on CL. Some go longer, some die earlier. They're pretty easy to change if they go bad at least, just that bolt on the back of it is hard to reach.

 

Mine went out last year at 75,000 miles. Had a suspicion beforehand that it was going to fail. I noticed a slight burning smell in the area of the alternator.

 

A very simple replacement DIY, reconditioned units are sold everywhere. If you want brand new then go to Toyota.