Rob,

I agree with your comments. MTBF for vacuum pumps seems to be about 500 hours per the Parker SB's and SDR info. As to TCAS and midairs-- there are about 10-20 midairs a year. Half of those occur in the pattern on final approach at less than 500' AGL. TCAS is not going to prevent those. Assess your risk-- flysmart.

Jeff Edwards