11 Mar 2017, 06:59
Yes, to both your questions (reeds age, and magnets degrade, as does everything, even us). It's called Entropy, and it is the Order of Things in this Universe.
The Reed/Magnet setting system was very clever, as it eliminated the need for multiple holes (and their associated seals) in the case, through which stems and crowns would have to pass. But, they discovered that it is very difficult to construct a solution for a problem that does not create other (sometimes worse) problems.
Magnets can be damaged in three different ways. First, exposure to high temperature (typically, several hundred degrees C; the so-called Curie-point, at which a magnetic material loses its' magnetic field). Not a likely scenario, for these magnets. Second, exposure to an intense external field. This can alter the field strength (up OR down) and polarization (direction of N-S orientation). Third, being subjected to a powerful mechanical shock (on the order of dozens to hundreds of G's). "Permanent" magnets can only lose, never gain, field strength in this way. It has been correctly pointed out that field polarization is critical for reliable actuation of switches (both types).
With the right equipment, setting magnets CAN be successfully re-polarized. Note: button magnets are also subject to the above influences.
Reed switches have their own set of potential ills. They were the real weak point in the Time Computer design, being little more than thin glass tubes enclosing paper-thin slivers of metal. Though potted in silicone rubber to enhance their resistance to high-G shocks, such events could still (A) Break the glass, or (B) Bend one or both of the contact leaves, which could (A) Render the switch completely inoperative, (B) Cause the switch to latch (so a function stayed on continuously), or (C) Increase the separation between the leaves so a button or setting magnet could not close them. There is no "repair" for these conditions; damaged or defective switches must be replaced. Note: Setting switches require a stronger magnetic field to close (otherwise, it might be possible to trigger a setting function when pressing a demand button), so a setting switch should never be used to replace a demand switch (the chance of it working properly...or at all, approach zero). If at all possible, reeds should always be replaced with one of like type. Secondary Note: In an attempt to expedite replacement of reeds, demand switches were sorted by field-strength-needed-to-actuate, in three levels..."standard", "low", and "high". Standard switches were unmarked, "low" was green, and "high" was red...the origin of the dabs of red and green paint on the ends of some switches. For example, if a watch came in with a damaged Time reed that was marked red, they were vastly more likely to get an acceptable match to the button magnet on the first try with another red-marked switch, rather than a random swap; this has saved me no end of time (and frustration).