Very old sourdough starter; how long is too long? For quite some time, my grandmother has had a sourdough starter kept in the fridge. I observed her making muffins and whatnot on an infrequent basis, with the intervals sometimes increasingly greater than the 14 days I see recommended on various sites. My first question is did I just miss her "washing" the mix or is there a secret way to store the starter long term that I am not observing?

The jar has been stored in a static location in the back of the fridge, and is mostly full with a clearish layer (presumably the alcohol layer), apparently airtight, and without noticeable discoloration. With my grandmother's increasing age and decreasing health I doubt this has been touched in between one and two and a half years. 

My second question is what beyond obvious (pink, blue, green) color changes am I looking for that tell me that I have to chuck this and start over?

My third question is if I do not get any "stop" signs (from question two) what would the best way to extract a viable sample for my own mix without contaminating or making significant modification to the existing jug? My first thought is to us the trick where you put your finger over the top of a straw to lift out a liquid. And then can I just pick up where I am reading elsewhere about washing and resurrecting old starters? 

Thank y'all for your help!
I had two that I neglected for 8 years in my fridge. I thought several times about tossing them. 

Glad I didnt! 
I recently washed &amp; fed both several times and they are alive and well. Totally amazing how durable they are.