I personally find long term to be at least 2 years where I hold my coins without touching them.
3 months to 1 year is a mid length investment
Over 1 year is a fairly long term investment
3 years + Example holding on to oil stocks until the economy picks up again and those shares start rallying is a long term investment.
Bitcoin anything over a week is a long term investment if your trading lol.
I somewhat agree, to me a year of holding bitcoins or anything else is a long term but maybe that's because I don't have too much to put aside, therefore I can't keep something away for a long time. I guess its different for different individuals, what one may consider to be short term, it may not be the same for someone else.