Aside from the lower/upper radiator hoses, which have been replaced at least twice; how often should the little hoses - seems there are several be replaced??

I have 122K and have had several radiator flushes performed by a mechanic I highly trust; will be doing another flush here soon, but have never had a leak at any of the small hoses, thus they are original. Should this just be something I do?

Likewise, I've never had a prob with the thermostat, as far as I know it's original too - however it IS going to be replaced this time.

You must be referring to the heater hoses. Yes, you should replace those. Also, make sure you test that new themostat before you install it. I've had several bad ones right out of the box.