what is "long term"? Five seconds, 5 days, 5 years, 5,000 years?
There is a daily cycle you have to worry about. Then a monthly cycle. If you get over that then it is probably OK for about 6 months.
The problem is as I have said before that there are so many variables you can't answer this question. No one can. There are too many variables and it is impossible to see how they all interact.
In engineering terms putting 20' of wire in front of a high impedance analogue input is too much. It will not work reliable. That means for every person in every location, for all weather conditions for ever. If you were trying to see this as a piece of professional kit then it wouldn't meet any standard you threw at at.
Yes you can do it once for a video as a demonstration but what happens is that you will try it and then come back on the board saying that it sometimes resets your arduino or that it sometimes fails to trigger or a host of other intermittent stuff.