The ACARS function is there to be used. Common sense is the word, though. I've seen guys requesting the weather for every possible airport en route, even when you can see their runways from 500 miles away.
Many moons ago I was told by one SMNC that it cost 37 cents of a US dollar per request. The use of ACARS was never an issue here, but some newbies keep raising these questions. Those costs are basically none of our business.