How often does the timing belt need to be changed

At least every hundred thousand mile,s,

http://www.samarins.com/reviews/altima_07.html says both the I4 and V6 have a timing chain

FordNut is correct. Nissan has used timing chains on the 4-cylinder and 6-cyliner Altimas since 2002. They are designed to last the life of the engine but, unfortunately, sometimes they don't. The good news is that they are not prone to just snap like a belt and they normally give you plenty of warning before failing as they will start making progressively more noise.

When a timing chain is about to go out, is there a clicking noise?? I'm trying to diagnose a ticking noise that sounds like barrons or a series of clicks then it stops. Not sure what it is.

No a chain will stretch and then it will get to the point it will skip over a tooth on the sprocket and timing will then be off and the car will not start. Also may cause wetting of the spark plugs at this point.

Aa chain may get wear but it will not stretch

A timing chain will rarely fail, nor will it stretch. The usual failure with a timing chain is when the chain tension-er begins to fail. It is relatively easy to tell when the tension-er is begining to fail as your engine will begin to emit a sound like a blender on high speed.

How often mileage wise do I have to change my timing belt?

Every 100-110,000 miles or wait until you hear above sounds as it will not snap

It will snap!! I had an 2002 Altima and never any issues or noises and it broke and warped all my valves...it's super expensive to fix

I have a 2014 Nissan Sentra. When should I look a chain/belt , I have accumulated 104,200 miles on car right now.