Rare Earth magnets are magnets that are made out of the Rare Earth group of elements. The most common Rare Earth magnets are the Neodymium-Iron-Boron and Samarium Cobalt types.

There are 2 types of magnets: permanent magnets and electro-magnets.

Remanence Br: Determines the pull of magnet, the larger the Remanence the stronger the pull.<br />
  Energy product BH(max): determines the amount of magnetic material need for one design, The bigger the energy product is, the smaller the size of the magnet you need.<br />
  Coercivity Hc: The larger the coercivity, the stronger is the magnet's resistance to demagnetization.

Generally the magnet will experience a degradation in its physical properties, such as corrosion, prior to it demagnetizing because of age. However, If a magnet is stored away from power lines, other magnets, high temperatures, and other factors that adversely affect the magnet, it will retain its magnetism essentially forever.
 

Modern magnet materials do lose a very small fraction of their magnetism over time. For Samarium Cobalt materials, for example, this has been shown to be less that 1% over a period of ten years.

The factors can affect a magnet's strength:
a. Heat
b. Radiation
c. Strong electrical currents in close proximity to the magnet
d. Other magnets in close proximity to the magnet
e. Neo magnets will corrode in high humidity environments unless they have a protective coating.
Shock and vibration do not affect modern magnet materials, unless sufficient to physically damage the material.
 

Provided that the material has not been damaged by extreme heat, the magnet can be re-magnetized back to its original strength.

Once a magnet is fully magnetized, it cannot be made any stronger - it is "saturated". In that sense, magnets are like buckets of water: once they are full, they can't get any "fuller".

(1)Humidity and temperature should be controlled at dry and room temperature level. Applying some anti-rusty oil (machine oil) can protect uncoated magnet very well; Coated magnet should be insulated from air or vacuum stored.

Soft magnetic material can be used in shielding or insulating magnetic field, like the common steel or iron plate. Thickness of the plate should be considered carefully because too thin plate may be saturated and can only duct a part of flux of the field, that will make the shielding only partially, not fully. Permeability, size and shape will be the main factors to be considered when selecting the shielding material.
 

Sintered NdFeB magnet is very brittle but hard. Its magnetic field is very powerful that can generate a force of 600 times of its weight. Caution should be to handle the magnet to avoid any damages to human body or the magnet itself. Some necessary protection method should be adopted when handling big block magnets. During installation, some fixture must be needed.

Not easily or safely. Nd-Fe-B sintered magnets behave like a ceramic. They have tendency to crack and chip when drilled. Additionally, the powder produced when machining these magnets is flammable. Lastly, machining causes heat to build up in the magnet which may result in it being demagnetized. You need professional group to machine the exact NdFeB magnet for you, lot quantity, dimension and shape, and tolerance.

No. The Br value is measured under closed circuit conditions. A closed circuit magnet is not of much use. In practice, you will measure a field that is less than 12,300 Gauss close to the surface of the magnet. The actual measurement will depend on whether the magnet has any steel attached to it, how far away from the surface you make the measurement, and the size of the magnet (assuming that the measurement is being made at room temperature). For example, a 1" diameter Grade 35 Neo magnet that is 1/4"long, will measure approximately 2,500 Gauss 1/16" away from the surface, and 2,200 Gauss 1/8" away from the surface.

Either by fixturing  or gluing to combine magnet and other parts together. The assembling process should be completed by those experienced professionals. Our comapny has such experience of MRI, magnetic fridge installation. We have the ability to provide assembling service to all kinds of magnetic components.