And how much is a safety switch? And how often to they go out?
No, the problem is that people are used to thinking of zerks as part of the equipment, instead of recognizing them as consumables.
To answer your question - I have replaced 2 safety switches now. 1 on a machine with 264 hrs and one on a friends machine with under 300 hrs. That is the only two BX25's we have around so I am two for two and have read of others having the same issue for some reason. I still would not recommend everyone waste the $10 or so bucks to have one "just in case" however but if you need the machine well maybe it is worth it. Not really different then a $13 kit that many will never need them.
Now on the old b we had, L3700, B7610, KX91, MX5100 and my BX25 a well as several other machines I have only replaced a total of two zerks due to me damaging them...... I have bought and rebuilt a few pieces of Eqpt where the Zerk came to me broken and I replaced them (They were sheared off) but none of the larger eqpt ever consumed them in my case.
Not an argument but understand not everyone has or wants to keep spares of everything and it does not make them wrong. I personally keep a large supply of parts handy but I have friends and neighbors that don't for whatever reason. I know you mention they are not expensive and I don't disagree but start adding everything up - Zerks, various nuts/bolts - all lengths, metic, SAE, etc, Oil filters, air filters, different oils - reg, syn., hydro, etc, fuel filters, water filters, extra hydro hoses, different greases, etc and now do this for each and every machine and it does cost some real money, time and space....