Have never used any of the Mithril Coins I have. Have never bought any, either. Every one I have has been free (e.g. lottery, item conversion). Not something I plan to buy, and not something I will use for a "convenience". Only time I will even think of using a Mithril Coin is to get something tangible that I can still use years from now.
Turbine has made LOTRO a game where you can choose to spend either time or money to complete things or advance. This is just another way of giving you the choice of spending time or money. In this case the money is in the form of the Mithril Coin.
"Everyone's got one. Better to be a smart one than a dumb one." - me
"It's people like you that [I]think[/I] you know everything that give those of us that [I]do[/I] a bad name." - me
"Eat, drink, and be Merry, 'cause Pippin was a fool of a Took."