MOTM

Yes, I did my homework and searched the message archives and I found
no specific references to these questions, so here goes:

1.- I am now building a MOTM-420 which uses the SSM2220.  Is this part
or any MOTM part rare enough that I should be buying spares?

2.- I have not been putting any of the gerden-variety ICs in sockets,
just soldering them into the PCB.  I mean a 555 is worth what, $0.50?
 But what about the comparatively exotic SSM chips?

Am I unduly concerned?

PLL, BFG