Magnets loose their force after 400 years. So, it is not days or weeks. Do you realize what would happen if all people had free energy for their houses/cars/factories? You can't stop technology. Soon or later it will be reality.
400 year
It's spelled "lose", as in losing. Loose means large or unfit, as in yo pants drop off your ass.
http://www.magnetsales.com/design/designg_frames/designg_2.htm5.1 Time
The effect of time on modern permanent magnets is minimal. Studies have shown that permanent magnets will see changes immediately after magnetization. These changes, known as "magnetic creep", occur as less stable domains are affected by fluctuations in thermal or magnetic energy, even in a thermally stable environment. This variation is reduced as the number of unstable domains decreases. Rare Earth magnets are not as likely to experience this effect because of their extremely high coercivities. Long-term time versus flux studies have shown that a newly magnetized magnet will lose a minor percent of its flux as a function of age. Over 100,000 hours, these losses are in the range of essentially zero for Samarium Cobalt materials to less than 3% for Alnico 5 materials at low permeance coefficients.
5.4 Adverse Fields
External magnetic fields in repulsion modes will produce a demagnetizing effect on permanent magnets. Rare Earth magnets with coercive forces exceeding 15 KOe are difficult to affect in this manner. However, Alnico 5, with a coercive force of 640 Oe will encounter magnetic losses in the presence of any magnetic repelling force, including similar magnets. Applications involving Ceramic magnets with coercive forces of approximately 4KOe should be carefully evaluated in order to assess the effect of external magnetic fields.As I said before, because the magnetic field is stressed several times a second for these generator magnets, they are being slowly decayed and demagnetized. It seems that some magnets will decay in half their strength in 150 years just by sitting around doing nothing. However, most modern permanent magnets are produced by magnetizing iron alloys. The same very strong force that is used to make them can be slowly obtained while draining them in a generator described in your video. You are essentially spending energy to charge the magnets, and placing them as fuel in a motor where they are spent.
There were many many many generators built in the last 50 years and they work just fine for the first few weeks simply rotating in place without a workload. However once you attempt to use the energy to do useful things, the magnets weaken within days due to strong repulsive forces inside the engine and from alignment swings caused by passing by fields inside the rotation cycle.
Because the energy is expelled from the magnets, it keeps the generator spinning against basic friction forces. But it does not work, you get less energy than you put in, it costs more to charge, transport, install and spend the magnetic fuel than to use the energy directly. This is how our Universe works, until you can prove otherwise and win a freaking Nobel prize, you are talking out of your ass.