I would LOVE to do that. But the tanks are so bloody expensive. 30 bucks for a tank and ~17 bucks to fill. And the new ones need to be purged first...requiring an additional fee at most places.
If I could get them cheap enough, I'd convert my generator to propane and I'd be set. But 50 dollars or more per unit. Too much. Check the date of manufacture on the pair you got for 15 bucks. After 12 years they won't refill them.
I check all that now before buying...I made a mistake on the first couple tanks I bought.
I checked these two, both are full of gas, one is refillable and one isn't. At $7.50 a tank...that's a steal.
I've never paid more than $8.00 per tank, empty or partially full. I have a local guy who will 'top-off' my partial tanks for $1.00 a pound.
I can also refill the one pound Coleman lantern bottles from these tanks...just requires a special fitting.