I have three 5-lb tanks, one 10-lb and one 20-lb. There is a place near me that does hydro testing and filling but you usually have to go back the next day to pick the tanks up... even on a refill. My closest LHBS started filling tanks while you wait which is nice. Also, a number of times that I brought in a tank, she would just fill them and it seemed like they didn't even check the date. Once I went in and a guy said, "Nope, the tank is out of date" and I explained that the owner would fill it even if the tank date was expired and so he did fill it. Another time I went in for supplies and they flat-out said no to another guy with an expired tank. So now one of my fivers and my ten is out of date. I took them to the place to hydro test. $61 for the fiver and $63 for the ten. I believe that's $40 for the test and then $21 for the fiver and $23 for the ten for the refill. That's spendy. They will both be ready tomorrow so I suppose that's good.
Does anyone think that an out-of-date tank is dangerous to fill? Do these things concern you brewers or do you assume that with gentle handling they're good for longer than 5 years?
Also, I know this is common knowledge but greasing up the main (big) o-ring on your kegs every time you fill them has solved ALL of my questionable CO2 leak issues. Ever since doing this my tanks last a LONG time before needing a refill.