Shoe Inserts

I keep my inserts around until they start to break down.

My last pair of custom orthotics lasted about ~2 years before they needed to be replaced.  I use them in both my running shoes, and my everyday shoes. 

Wondering what type of orthotic? Most custom orthotics will say around 3-5 years average use.
Active people who do some real mileage out there, and then use them for everyday shoes as well,Im guessing you can cut that back to a few years best, but they are all different to some degree. Your feet should tell you if they're holding up. A constant orthotic wearer can usually feel a colapse in the arch from a crack in the plastic etc..
Your podiatrist can usually inspect them to see if they need replaced.
I think you should be fine to transfer them over to another shoe, but for me, not all shoes work well with my orthotics, its trial and error sometimes with these things.

cool!   They still feel very good.  They have little wear on the underside where they were rubbing on a hard edge of the shoe.   I only use them in my running shoes,  so I think they are good to go for a while longer.